Wireless Network Camera Systems

ABSTRACT

Apparatus, systems and techniques associated with battery powered wireless camera systems. One aspect of the subject matter described in this specification can be embodied in a system that includes a battery powered wireless camera including an internal battery to provide energy and a burst transmission unit to transmit information during burst periods. The system includes a base station, separated from the battery powered wireless camera, in wireless communication with the battery powered wireless camera to receive information from the battery powered wireless camera. The base station is configured to process the received information and includes a web server to transmit the processed information to a client. Other embodiments of this aspect include corresponding systems, apparatus, and computer program products.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.12/515,691, filed Feb. 19, 2010, which is a national stage applicationof and claims the benefit of International Application No.PCT/US2007/085308, filed on Nov. 20, 2007, which claims priority to U.S.Provisional Application Ser. No. 60/896,158, filed on Mar. 21, 2007 andU.S. Provisional Application Ser. No. 60/866,587, filed Nov. 20, 2006.The disclosure of the entire prior listed patent applications isconsidered part of the disclosure of this application and isincorporated by reference.

BACKGROUND OF THE INVENTION

This disclosure generally relates to providing battery powered wirelessnetwork camera systems.

Network camera systems can be based on the Internet protocol (IP) anduse Ethernet based networking technology. In some applications, networkcamera systems are replacing analog closed circuit television (CCTV) dueto various factors, such as accessibility, ease-of-use, cablingscalability, and lower cost of deployment and operation. With theubiquity of wireless networks such as WiFi networks (based on IEEE802.11 standards) and the emerging WiMAX networks (based on IEEE 802.16standards), wireless network camera systems are gaining popularity andare expected to become the dominant platform for video surveillanceapplications.

In an IP surveillance environment, the network camera system can includeIP cameras connected via twisted pair cabling to a network switch.Alternatively, the network connection can be achieved using wirelesslocal area networking (LAN) technology; e.g., the IEEE 802.11b standard.In various applications, IP cameras can include a web-server capabilityand remote clients or observers connected to the camera via standardTCP/IP interface standards such as FTP or HTTP. IP based network camerasystems can be designed using commercial off-the-shelf (COTS) componentsfrom a diverse number of suppliers.

BRIEF SUMMARY OF THE INVENTION

This specification describes various aspects relating to battery poweredwireless network camera systems, apparatus and methods of providing suchsystems. For example, the systems, apparatus and techniques describedherein can be implemented in ways that provide wireless IP video systemsthat require no power cable and can potentially operate on standardoff-the-shelf battery solutions for over a year. In addition, thesystems, apparatus and techniques described herein can be implemented inways to resolve the interference, interoperability and reliabilityproblems currently associated with existing wireless camera systems.

One aspect of the subject matter described in this specification can beembodied in a system that includes a battery powered wireless cameraincluding an internal battery to provide energy and a burst transmissionunit to transmit information during burst periods. The system alsoincludes a base station, separated from the battery powered wirelesscamera, in wireless communication with the battery powered wirelesscamera to receive information from the battery powered wireless camera.The base station is configured to process the received information andincludes a web server to transmit the processed information to a client.Other embodiments of this aspect include corresponding methods,apparatus, and computer program products.

Another aspect of the subject matter described in this specification canbe embodied in a wireless camera system which includes a battery poweredwireless camera including an internal battery to provide energy and aburst transmission unit to transmit information during burst periods.The system also includes a base station, separated from the batterypowered wireless camera, in wireless communication with the batterypowered wireless camera to receive information from the battery poweredwireless camera. The base station is configured to process the receivedinformation and including a web server to transmit the processedinformation to a client, and the base station is powered by a powercable connected to an external power source. The burst periods aredetermined based on at least one of a wireless link channel averagebandwidth capacity, a fidelity of images transmitted, and a latency ofestablishing and terminating a wireless connection between the batterypowered wireless camera and the base station.

A further aspect of the subject matter described in this specificationcan be embodied in a system that includes a base station which includesa first receiver configured to receive information in a first wirelessnetwork and a second transmitter configured to transmit information in asecond wireless network. The system also includes a remote node whichincludes a first transmitter configured to transmit information in thefirst wireless network and a second receiver configured to receiveinformation in the second wireless network. The second transmitter isfurther configured to transmit control information from the base stationto the remote node via the second wireless network and the firsttransmitter is further configured to transmit compressed videoinformation from the remote node to the base station via the firstwireless network. Additionally, the second receiver in the remote nodeis further configured to operate for substantially longer period of timethan the first transmitter in the remote node. Furthermore, the secondreceiver in the remote node can be configured to operate continuouslyfor periods of time exceeding 5 hours while drawing less than 10 mW ofpower.

Yet another aspect of the subject matter described in this specificationcan be embodied in a method that includes transmitting information, byone or more battery powered wireless cameras having internal batteriesin a wireless link. The transmitting of information during burstperiods. The method also includes receiving information by a basestation, and the base station includes a web server. The method furtherincludes processing the received information in the base station, andtransmitting, by the web server, the processed information to a client.

In another aspect, a wireless camera system includes a battery poweredwireless camera having an internal battery to provide energy and a bursttransmission unit to transmit information during burst periods. Thesystem also includes a base station, separated from the battery poweredwireless camera, in wireless communication with the battery poweredwireless camera to receive information from the battery powered wirelesscamera. The base station is configured to process the receivedinformation and the burst periods are determined based on at least oneof a wireless link channel average bandwidth capacity, a fidelity ofimages transmitted, and a latency of establishing and terminating awireless connection between the battery powered wireless camera and thebase station.

In a further aspect, a wireless camera system includes a solar poweredwireless camera that includes at least one solar cell. The system alsoincludes a base station, separated from the solar powered wirelesscamera, in wireless communication with the solar powered wireless cameraand configured to receive information from the solar powered wirelesscamera. The base station is further configured to process the receivedinformation and includes a web server to transmit the processedinformation to a client.

In one aspect, a wireless camera system includes a battery poweredwireless camera that includes a power unit for energy source and a bursttransmission unit to transmit information during burst periods. Thesystem also includes means for determining the burst periods fortransmission of information. The system further includes a base stationconfigured to receive information from the battery powered wirelesscamera and to process the received information. The base stationincludes a web server to transmit the processed information to a client.The system additionally includes a first wireless link configured toconnect the battery powered wireless camera and the base station.

In another aspect, a network camera includes a networking moduleconfigured to communicate with a network. The network camera alsoincludes an image capturing module configured to capture images. Thenetwork camera further includes an image compression circuit configuredto compress the captured images. The network camera additionallyincludes a privacy lens cap or a visible shutter configured to enhanceprivacy and prevent the image capturing module from capturing images.The network camera can be a wired or a battery powered wireless camerathat includes an internal battery.

In yet another aspect, a network camera includes a burst transmissionunit configured to transmit information during burst periods and anetworking module configured to communicate with a network. The networkcamera also includes an image capturing module configured to captureimages. The network camera further includes an image compression circuitconfigured to compress the captured images. The network cameraadditionally includes a privacy lens cap or a visible shutter configuredto enhance privacy and prevent the image capturing module from capturingimages. The network camera can be a wired or a battery powered wirelesscamera that includes an internal battery.

These and other embodiments can optionally include one or more of thefollowing features. For example, a plurality of cameras can beassociated with one base station. A plurality of cameras can beassociated with two base stations to provide redundancy in case one ofthe base stations fails. Furthermore, a plurality of cameras can beassociated with a plurality of base stations in a mesh architecture tomaximize redundancy, resiliency and low power operation. The internalbattery can be configured to provide energy without a power cableconnected to an external power source that is external to the camera.

The base station configured to receive information from the one or morebattery powered wireless cameras can include scanning one or morecommunication channels for channel availability between the base stationand the one or more battery powered wireless cameras; obtaining anavailable channel for data transmission based on the scanning of channelavailability; and associating the available channel with a specific oneof the one or more battery powered wireless cameras. The associating ofthe available channel can include reserving the available channel for apredetermined period of time, and assigning the reserved availablechannel to the specific one of the one or more battery powered wirelesscameras. In addition, during the predetermined period of time, theavailable channel can appear to the other one or more battery poweredwireless cameras as unavailable for wireless communication.

Each of the one or more battery powered wireless cameras can include ascanning circuitry configured to scan the one or more communicationchannels for channel availability and to determine available channelsfor data transmission. Each of the one or more battery powered wirelesscameras can also include a storage device configured to store data whenthere are no available channels for data transmission. The wirelessnetwork camera system can also include a network connecting the basestation and the client, and the client can include a video surveillanceapplication to display video images. The network can be one of a wiredEthernet network, or a wireless network such as a WiFi network or aWiMAX network. The transmitted information can include compressed videosignals or digitally encoded video signals.

Each of the one or more battery powered wireless cameras can include animage sensor configured to produce an image; an image compressioncircuit configured to compress a digital file of the image produced bythe image sensor; and a substrate configured to monolithically integratethe image sensor and the image compression circuit. The burst periodscan be determined based on at least one of a wireless link channelaverage bandwidth capacity, the fidelity of images transmitted, and alatency of establishing and terminating the wireless link. The burstperiods can be further determined based on a trigger event caused by oneof a sound detection, an infrared motion detection, an ultrasonicdetection, a radio signaling circuitry, and a channel availability fordata transmission.

The wireless network camera system can include a first wireless networkconfigured to communicate between the one or more wireless cameras andthe base station via one or more high-bandwidth channels. The wirelessnetwork camera system can also include a second wireless networkconfigured to communicate between the one or more wireless cameras andthe base station via one or more low-bandwidth channels. The secondwireless network can be configured to be more reliable and/or moreavailable (e.g., operates for a longer period of time) than the firstwireless network.

Both the first and second wireless networks can be one of a wirelessEthernet network, a WiFi network, and a WiMAX network. In addition, boththe first and the second wireless networks can be based on Multiple InMultiple Out (MIMO) technology. The second wireless network can beconfigured to operate for an extended period of time to facilitate oneor more of set-up, installation, and troubleshooting activities. Thesecond wireless network can also be used to signal to the one or morewireless cameras that one of the one or more high-bandwidth channels isavailable for data transmission. The channel availability information ofthe one or more high-bandwidth channels can be determined by processingin the base station.

The base station can include a transmitter configured to transmit viathe second wireless network information that includes one or more ofpositional, zoom, and tilt commands to each of the one or more wirelesscameras. The base station can also include a transmitter configured totransmit via the second wireless network a command to flush informationand data stored on each of the one or more wireless camera through thefirst wireless network. Each of the one or more battery powered wirelesscameras can include a high-bandwidth transceiver and a low-bandwidthtransceiver.

The high-bandwidth transceiver can be configured to receive informationvia the first wireless network and the low-bandwidth transceiver can beconfigured to receive information via the second wireless network. Thelow-bandwidth transceiver can be configured to consume less than 4 mW ofpower in constant operation or operate in a polling mode that reduces anaverage energy consumption of the camera. The base station can includetiming circuits configured to be synchronized with the cycle of thepolling mode in the receiver.

Each of the one or more battery powered wireless cameras can include astorage device configured to store the information at a first fidelity.The information can be transmitted to the base station at a secondfidelity, and the first fidelity is different from the second fidelity.The one or more wireless cameras can be configured to be powered up toobtain information in response to a trigger event caused by one of asound detection, an infrared motion detection, an ultrasonic detection,a video processing based movement detection, a relay switch, a microswitch, and a radio signaling circuitry. Each of the one or morewireless cameras can further include a storage device configured tostore captured information for a predetermined period of time. Thestored captured information can be transmitted to the base station inresponse to a trigger event.

Each of the one or more wireless cameras can include a first switchconfigured to control one or more of operation in darkness, operationbased on sound detection, operation based on infrared motion detection,operation based on ultrasonic detection, and operation by triggers; anda second switch configured to indicate operation duration of the one ormore wireless cameras. A frame rate can be obtained based on theoperation duration so that the internal battery can last substantiallyfor the operational duration indicated by the switch.

Each of the one or more battery powered wireless cameras can furtherinclude an uncompressed image capture module configured to operate basedon periods that are different from the burst periods. The image capturerate and the burst transmission rate can be based on motion detection,and further wherein when motion is detected in the captured images, theimage capture frame rate is increased, and when motion is not detectedin the captured images, the image capture frame rate is decreased.

The internal battery of the wireless camera can be based on one or moreof solar cells, fuel cells, galvanic cells, flow cells, kinetic powergenerators, and environmental energy sources. The internal batteryoutput voltage can be boosted or regulated by an active power managementcircuitry. The internal battery can be recharged by one or more of solarcells, fuel cells, galvanic cells, flow cells, kinetic power generators,and environmental energy sources. The internal battery can include anarray of rechargeable battery cells configured to extend the useablelifetime of the rechargeable array to be greater than a lifetime of asingle rechargeable battery cell, and less than the entire array ofrechargeable battery cells are used at a given time.

The useable lifetime of the internal battery can be extended bycontrolling the current withdrawal of the rechargeable battery cells towithin a predetermined current limit. The controlling of currentwithdrawal from the internal battery can be performed through a highefficiency regulation circuit that includes a switching regulator fordrawing a limited current flow from the battery cells, and a capacitorfor temporary storage of energy. The internal battery can be replaced bya high capacity capacitor and a charging circuitry associated with thecapacitor. The internal battery can include at least a high capacitycapacitor and a rechargeable battery.

Each of the one or more battery powered wireless cameras can include acompression module configured to operate based on periods that aredifferent from the burst periods. Each of the one or more batterypowered wireless cameras can capture and transmit audio information andsensor information. Each of the one or more battery powered wirelesscameras can be surface mountable and can include a housing that has asolar panel configured to recharge the internal battery.

Particular aspects can be implemented to realize one or more of thefollowing potential advantages. An architectural change in the wirelesscamera can be implemented to obtain significant power savings inwireless network camera systems. Such a design change can offersubstantial power savings over commonly understood power-reducingtechniques such as using more efficient electronic components in theradio transceivers, image capture, and compression integrated circuits.

An ultra-low power wireless camera can be obtained without compromisingthe ability of new and existing client system to access data usingstandard IP connections and standard or de-facto application programminginterfaces (APIs). In particular, the base station code can comply withwell established IP camera API's. Additionally, even though the wirelesscamera can operate at an ultra-low average power, during the burstperiod when the camera is transmitting data to the base station, thecamera can allow for power consumption in excess of 100 mW. This is incontrast to existing wireless sensors which will typically consume lessthan 100 mW of power when transmitting data.

Multiple wireless cameras (e.g., up to 16 wireless cameras) can beassigned to a single base station. The base station and wireless cameracombination can deliver all the intelligence and features expected for acommercial grade IP camera solution. The solution integrates intoexisting IP networks and exposes standard video monitoring applicationinterfaces so that popular video surveillance data applications can beused. This makes for rapid, seamless and pain free deployment. From thenetwork perspective, the combo processing ensures that all wirelesscameras appear to be 100% compatible IP cameras. Video can be deliveredcompressed to industry standard format such as MJPEG or MPEG-4, ready tobe accessed and managed by industry standard software.

The base station can connect to a regular wired Ethernet LAN and on tothe Internet, just like any IP surveillance system. A seamlessintegration can occur over a standard 802.11b/g/n wireless Ethernetnetwork. Since it can be wireless to the Internet access point, thedistance range of the wireless network camera system can be as wide astoday's wireless systems. The user can perform a walk-through wizardonce, and begin installing multiple security cameras anywhere within therange of the base station.

Further, a battery powered wireless camera operation can be achievedusing well established components. Battery powered wireless networkcamera systems can be achieved without additional external power sourceor cabling. These systems can have standard web server capability forclient access to the captured data. Because no power cabling is needed,these battery powered wireless network camera systems can be deployed inlocations where previously difficult to service. Camera operation forextended periods of time can be obtained using small battery packs.

By using modified media access techniques, unreliable or inconsistentconnectivity associated with the standard IEEE 802.11 wireless links canbe avoided. Additionally, the erratic set-up and/or operation of awireless link due to interference or other environmental factors can beminimized. The drawbacks of the IEEE 802.11 MAC standards in poorconnection conditions can be overcome by observing interference and alsousing techniques to reserve and hold a connection for data transmission.For example, by implementing a second low-bandwidth radio/transceiver inthe wireless camera, the modified media access techniques can betriggered and controlled through the second radio. The low-bandwidthradio can establish a link in conditions where the high-bandwidthradio/transceiver cannot.

By incorporating more functionality in the base station of the wirelessnetwork camera system, the base station can detect and correct linkproblems by requesting retransmission of the captured data. Such requestcan be sent via the low-bandwidth radio which can be more reliable anduse lower power than the high-bandwidth radio. This retransmission canbe hidden and transparent to the client surveillance application throughthe virtual web server or relay server in the base station. In addition,image and video analytical functions such as object recognition, peoplecounting, and license recognition can be implemented in the base stationrather than the camera. These analytical functions can be implemented ina hidden way so that it logically appears to the client that thesefunctions are occurring in the camera. Furthermore, in applicationswhere privacy of the image or audio data needs to be protected, the datatransmitted wirelessly can be encrypted.

The specific aspects may be implemented using a system, method, or acomputer program, or any combination of systems, methods, and computerprograms. The details of one or more embodiments are set forth in theaccompanying drawings and the description below. Other features,aspects, and advantages will be ascertained from the description, thedrawings, and the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other aspects will now be described in detail with referenceto the following drawings.

FIG. 1 is a block diagram of a battery powered wireless camera.

FIG. 2 shows a battery powered wireless network camera system for remotesurveillance applications.

FIG. 3 shows another battery powered wireless network camera system forremote surveillance applications.

FIG. 4 is a diagram showing a burst data transmission.

FIG. 5A shows a flow chart of a MAC algorithm that can be used by thewireless camera.

FIG. 5B is a flow chart showing a process that can be used to implementthe CTS-to-Self algorithm.

FIG. 6 shows a block diagram of a battery current limiting circuit thatcan be used to connect to the camera power input.

FIG. 7 is a block diagram of computing devices and systems.

Like reference symbols in the various drawings indicate like elements.

DETAILED DESCRIPTION OF THE INVENTION

The systems, apparatus and techniques described herein relate toproviding wireless network camera systems. For example, the wirelessnetwork camera systems described herein can operate for an extendedperiod, e.g., months or even years without maintenance in certainapplications. By looking at the energy requirements of the system overtime, the systems and techniques described herein use a time-slicedenergy cycling technology to distribute processing needed over time andlocation. Furthermore, the systems and techniques described herein arecombined with modern, available wireless technologies (such as themodulation schemes deployed in systems like WiFi 802.11) andoff-the-shelf advanced semiconductor components. As a result, an overallreduction in the camera power of two or more orders of magnitude can beachieved. For example, the wireless camera described herein canpotentially operate on less than 10 mW of power on a sustained basis,and the wireless camera can run over 12 months using 10 AA Lithiumbatteries.

Connection from the base station to other IP security video cameras andnetwork can be done via wired or wireless links. Each wireless cameraconnected to the base station can be assigned an IP address from theEthernet router through the regular DHCP or other standard Ethernetmethods. Further, each wireless camera in the network behaves like aregular IP camera to any existing client or application on the LAN. Inthis way, each wireless camera can be addressable through industrystandard APIs so that each video stream and each wireless camera can beviewed, recorded, and manipulated individually without any modificationsto existing applications and hardware.

The wireless network camera systems described herein can be used innumerous applications, such as alarm verification and surveillanceapplications for constructions sites, mobile transportation, and borderpatrol.

Construction Sites

Construction theft is widespread and nothing new, but the amount oftheft is increasing. Construction thefts, which are rarely solved, canlead to construction delay, higher costs and insurance rates, and higherhome prices. The National Association of Home Builders estimates thatthe construction theft problem costs the US building industry $4 billionannually and increases the cost of the average home by 1.5 percent. Somebuilders try to protect themselves by using bind tools and materialsinto heavy heaps or block driveways. Most install temporary locks onwindows and doors and wait until the last minute to install appliances.

Installing traditional video security cameras can be difficult becausepower is unlikely to be available at the location best served by thevideo camera. Most builders are unwilling to invest the dollars for atemporary installation. In addition, cabling for a network camera systemcan be impractical at the construction site. The wireless network camerasystems described herein can offer a solution to this problem. Wirelesscameras can be quickly added and moved during the construction phase,and theft activity can be identified in real-time. Since the cameras aretemporary, the builder can re-use the cameras at other new constructionsite, decreasing the initial investment for a total security system tocover all construction projects.

Mobile Transportation

Without proper measures, public transit vehicles, school buses, lightrail cars, and trains can be affected by security issues involvingpassengers and operators. Problems such as vandalism, assault and evensuspicious liability claims can affect or disrupt an operation. Whilethere are mobile surveillance systems, they require an on-board DVRwhich can be cumbersome and difficult to retrofit into an existingtransportation vehicle. In addition, the existing system may not providereal-time information to a central monitoring station. The wirelessnetwork camera systems described herein can alleviate this problem witha low installation cost, and very little additional equipment toinstall.

With protected dome cameras at multiple locations on the transportationvehicle, a broad coverage can be enabled, while providing an avenue forcentral monitoring through a 3G IP based data network. The base stationcan store images temporarily should an interruption occur through the 3Gnetwork preventing immediately transfer of images. With the temporarystorage at the base station, a near real-time video security monitoringcan still be obtained with a very cost effective system. Video recordingcan be done at the central location, providing the benefits of immediateaccess to security officials, elimination of daily video transfer forhistorical recordkeeping and leveraging lower storage costs at thecentral facility.

Military and Border Patrol

In a war zone, there is no time and too much risk to install videosurveillance systems. In terms of security, there is no greater needthan in military applications for quick, reliable and secure mobilevideo security systems that can be centrally monitored. Lives can besaved in identifying rogue activity and quickly responding topotentially dangerous scenarios before an enemy can act. In most regionsof interest, there is no power availability and the lack of asurveillance capability can be detrimental to securing the perimeter. Ifa security threat cannot be identified and responded to before it is toolate, then the effort for enforcing barriers and preventing unauthorizedaccess can be severely hampered. Using the wireless network camerasystems described herein, the perimeter can be visually monitoredwithout risk to military personnel.

With the vast expanses that a border patrol monitors, it is impossibleto visually monitor all activity using border patrol agents. Using thewireless network camera systems described herein, remote monitoring ofborder regions can be achieved. A larger number of vital regions of theborder can be monitored for unauthorized access using the same number ofborder agents, providing cost savings while improving efficiency. Byintegrating internal video analytics software, dynamic frame and bitrate control (e.g., allowing for slower frame and bit rates when nothingis happening, but switching to faster frame and bit rates for improvedvideo quality during critical events), and satellite IP access into thebase station, border regions can be covered.

Mining and Underground Applications

Underground mine safety has emerged as a pressing issue worldwide.Various countries and states have begun using communication technologiesto improve mine safety. One primary objective is to maintain andascertain the health and well-being of mining personnel during normaland emergency conditions. New technologies are applied to address voicecommunications, however, video surveillance and monitoring can provideadditional avenues to increase safety. Furthermore, video surveillancecan be used to gather information and improve the efficiency and reducedown time for mining production. However, the inherent nature of miningis not conducive to wired camera deployment. The wireless camera systemdescribed herein can be implemented to monitor underground and mining byvideo surveillance.

Difficult Environments

In many environments (e.g., near or under water or hazardous chemicalenvironments), access to wired power supplies can be difficult if notimpossible. One example can be the environment in and around swimmingpools. In such environment, wireless camera systems described herein canbe implemented to monitor pool safety by video surveillance.Additionally, in a chemical plant or processing plants where caustic orhazardous material conditions may not allow power cabling to exist orwhere the installation of power cabling may be impractical, the wirelesscamera system described herein can be implemented to monitor plantsafety by video surveillance.

Alarm Verification

Due to the number of false alarms created by security systems, manypolice departments are reluctant to respond to alarms unless there hasbeen “visual verification” that the situation merits a response. Thewireless network camera systems described herein can provides an easy toinstall (no power needed) camera system to allow for remote visual alarmverification

FIG. 1 is a block diagram of a battery powered wireless camera 100 for awireless network camera system. One energy-saving feature of the batterypowered wireless camera 100 is that the web server has been removed fromthe camera 100 itself By not having the web server functionality in thewireless camera 100, the camera 100 need not constantly be ready torespond to access from remote clients, which access the web server toinitiate data transmission. In one implementation, the wireless networkcamera 100 can be powered for many months using an internal battery 102.The battery 102 can include, e.g., solar cells, galvanic cells, flowcells, fuel cells, kinetic power generators, or other environmentalenergy sources.

Battery powered wireless network camera operation can be achieved, forexample, at full-motion frame rates in excess of 10 frames per second ata resolution of 320×240 pixels. The wireless camera 100 can be connectedthrough a wireless network 150 with a base station 160. The wirelesscamera 100 includes a high-bandwidth radio frequency (RF) transceiver104 and a low-bandwidth RF transceiver 106 for communicating with thebase station 160 through the wireless link 150. The wireless camera 100also includes a central processing unit (CPU) 110 for controllingvarious functionalities associated with the camera.

In certain implementations, the CPU 110 can be replaced by a simplifiedmicro-coded engine or state machine, or a hard-coded state machine. Forexample, the micro-coded engine or state machine can be similar to thatof an RF ID tag with limited response to input. This is because thewireless camera 100 can perform a limited number of predefine functionsand those functions can be programmed into the micro-coded engine orhard-coded state machine. In this manner, the power requirement and thecost of the camera can be reduced. In an alternative implementation,various components of the CPU 110 can be combined into a single ASIC,which integrates the entire active and some passive components andmemory in order to achieve power savings. Flash memory or other memorycomponents can be the only exceptions to this integration.

The CPU 110 includes a general purpose microcontroller 112 running alight real time operating system. Alternatively, in order to reduceoverhead the microcontroller 112 may not use an operation system. Themicrocontroller 112 can execute programs from an external memory such asa flash memory 114 external to the microcontroller 112 or from memoryinternal to the microcontroller 112. The CPU 110 also includes animage/video compression engine 116, which can perform proprietarycompression algorithms or a standard algorithms such as MPEG2, MPEG4,MJPEG, JPEG, and JPEG2000, and the like. Memory contained in the CPU 110(e.g., flash memory 114 or other memory devices) can store bothcompressed and uncompressed video.

In one implementation, the compression algorithm can generate data thatrelates to the relative visual importance of the compressed data bits.This data can be utilized by the forward error correction (FEC) sectionof the wireless radio (e.g. the high-bandwidth radio 104). The FECsection of the wireless radio can provide “un-equal protection” (UEP) tothe transmission of the compressed data as dictated by its importance.The complementary decoder can be implemented in the base station 160.This transmission scheme can achieve increased efficiency for thetransmission of the image data. One example of such transmission schemeis a publication by Yanjun Hu, et al. entitled “An Efficient JointDynamic Detection Technique for Wireless Transmission of JPEG2000Encoded Images.”

The CPU 110 also includes an audio compression engine 118. Memorycontained in the CPU 110 can store both compressed and uncompressedvideo, as well as compressed and uncompressed audio. Under low batteryor poor data radio channel bandwidth conditions, a relatively largeamount of energy can be saved by disabling the bulk high-bandwidth radio104 and not transferring the image, audio or other data to the basestation 160. In this mode, the flash memory 114 can be used to hold asignificant amount of data up to many hours until the data is retrieved.

In conditions where the radio transmissions are interrupted or jammed;for example, by an intruder, an alarm can be initiated silently from thebase station 160 to the external network or can be externally indicatedby visual or audible transducers activated on the base station 160 orwireless camera 100. In one implementation, alarms can be triggered ifdata transmissions fail for a specified amount of time. This failure indata transmission can be caused by an intentional jamming by an intruderor by a failure to establish a transmission link. In such situation, thewireless camera 100 can store images and/or audio data in a storageelement, such as a flash memory 114, for transmission or retrieval at alater time.

Data retrieval at a later time can be achieved by manually removing thecamera 100 or storage element from the camera 100 and connecting to aWindows, Linux or Macintosh based computer via a Universal Serial Bus(USB). The storage unit can appear to the computer to be a standard massstorage device with files of the captured data. In anotherimplementation, when there is a failure in data transmission, the systemcan use an alternative wireless connection to transfer data, forexample, such as operating on a different frequency, using differentmodulation methods, or by increasing the output power of the wirelesstransmitter.

The compression engines 116 and 118 can operate on captured data outputfrom the sensors connected to the CPU 110. Alternatively, thecompression engines 116 and 118 can operate on captured data temporarilystored inside the flash memory 114. In this manner, the compression andcapture processes can operate on independent cycles. This independencecan also help maximize energy efficiency. For example, the image capturemay be occurring 5 times a second, but the compression engine mayoperate at very high speed on multiple images every 3 seconds. In thisfashion, the energy requirements of starting up the compression engines116 and 118 can be amortized over a large amount of data. In oneexample, the flash memory 114 can hold approximately 15 uncompressedimages before the compression engine is activated.

In some implementations, most or all components of the compressionengines 116 and 118 can be integrated into the microcontroller 112 andperipheral blocks. In this way, the compression can be achieved in themicrocontroller 112 using a hybrid software and hardware accelerationfor computational intensive processing. Other alternatives for thecompression engines 116 and 118 can include a separate applicationspecific integrated circuit (ASIC) or a field programmable gate array(FPGA). An example FPGA can be one based on flash technology such asActel Corporation's Fusion product line, where the “instant on” allowsfor rapid start-up capabilities reducing energy wastage during thecycling process. Alternatively, the image capturing module 120 can havean integrated compression engine and output compressed data directly tothe CPU 110.

The CPU 110 can also perform the burst transmission store/control MACprocess needed to transfer the data transmission from the bulkhigh-bandwidth radio 104. The high-bandwidth radio 104 can be powercycled based on the physical layer characteristics of the radio andsustained bandwidth needed to maintain certain fidelity of the imagesand audio transmitted. The power cycling of the high-bandwidth radio 104is further described in more detail below.

In general operation, the microcontroller 112 can be started from a deeppower save mode by the clock 111, which can be, e.g., an ultra low powerreal time clock. The timing of this can vary depending on the aggregateneeds of the multiple processes as they cycle. Therefore, once poweredup the software can be used to initiate or manage one or more processesincluding image capture, data transmission, and image compression. Insome instances, the clock 111 can be replaced by a microcontroller withintegrated low power real time clock capability. An example of such amicrocontroller is the Texas Instruments MSP43O family of products.

In one implementation, most or all of the timing required for thewireless camera 100 can originate from the base station 160 and becommunicated to the wireless camera 100 through a secondary receiver(e.g., the low-bandwidth radio 106), as will be described in more detailbelow. This configuration can act as an alternative to using the clock111 described above, and allow for more of the processing complexity toreside in the base station 160. Additionally, the wireless camera 100can be simplified, cheaper, and more robust. Furthermore, the wirelesscamera 100 can consume less power because very little timing processingwould be needed in the wireless camera 100. In this way, the wirelesscamera 100 can act as a “slave” unit and the commands for the processingelements described below can be issued directly from the base station160.

In general, all the processing can operate on cycles independent of eachother to maintain maximum efficiency. Memory can be used to buffer databetween processes to allow for this. This buffering memory can be usedto ensure that data overrun or data under-run does not occur duringoperation. This buffering memory can be designed to operate at anextremely low power during non active or retention modes that can occurbetween processing cycles. This buffering memory can be distributedbetween some or all of various integrated circuits that constitute thewireless camera 100. Alternatively, a portion of the buffering can beconcentrated in specialized memory components. An example of this kindof memory component can be the Cypress Semiconductor Corporation's 16Mbit SRAM memory product CY62167EV18.

As shown in FIG. 1, a number of modules can interface to the CPU 110.The image capturing module 120 can include a low power imager such as aCMOS based sensor. Alternatively, a CCD can be used, but typically thesedevices use more energy than CMOS devices for a given frame rate,resolution and fidelity. The circuitry supporting the sensor can includememory to temporarily hold uncompressed images. In one implementation,image capturing module 120 can also include an image compression engineand memory that stores both compressed and uncompressed images. In someCMOS imagers, so called “active pixel” technology can be used to allowthe imager to power up and respond very rapidly to an image exposurecommand and then automatically power down.

In some implementations, the imager can have a number of active circuitsper pixel (such as analog to digital converters) to enable for rapidoperation for brief periods of time, followed by very low power standbyenergy consumption. This also means that the instantaneous powerconsumption of the imager can be relatively large during the framecapture and transfer process. In an alternative energy savingimplementation, the compression circuitry including the required memorycan be integrated directly onto the image capturing module 120 or evendirectly onto the image sensor die. This further integration can reducethe energy needed to transfer data and control information betweenintegrated circuits.

The sound detection module 122 can generate compressed or uncompressedaudio data. If uncompressed data is generated from module 122 then theCPU 110 can perform the compression. The sound detection module 122 canalso operate at low power, e.g., in the order of tens of micro watts andprovide a trigger output based on the noise level. The noise-leveltriggering event can be detection of a shock wave, detection of breakingor shattering glass detection or other similar acoustic detectiontechniques. In some implementations, the sound detection module 122 canoperate continuously and a positive noise trigger output can be used toactivate the wireless camera 100 from a standby mode. Once activated,the wireless camera 100 can initiate the various processing sections tostart cycling and, for example, start sending the surveillance data tothe base station 160.

In another noise-level triggering mode the sound detection module 122and the image capturing module 120 can continuously capture and store anon-going window of surveillance data of the immediately previousseconds, minutes or hours. During this time the bulk high-bandwidthradio 104 can be inactive in order to save power. However, once motionis detected some or all of the previously stored information can betransmitted to the base station or retrieved in other ways. This allowsthe activities that occurred in the area under surveillance prior to atrigger event to be investigated.

In a derivative behavior in this mode, different video compressionalgorithms operating at different rates can be used before and after thetriggering event. For example, JPEG, MJPEG or JPEG2000 type compressionalgorithms can be used during the pre-trigger period and MPEG2 or MPEG4type compression algorithms can be used during the post trigger period.This can avoid losing critical captured information on the activities inthe surveillance area in a time period leading up to the triggeringevent.

The infrared detection module 124 can operate at low power, in the orderof tens of micro watts, and provide a trigger output that indicatesmotion has been detected. For example, the infrared detection module 124can be implemented with a pyroelectric infrared sensor with a Fresnellens. In some implementations, the infrared detection module 124 canoperate continuously and a positive noise trigger output will activatethe wireless camera 100 from a standby mode. Once activated, thewireless camera 100 can initiate the various processing sections tostart cycling and, for example, start sending the surveillance data tothe base station 160.

The ultrasonic detection module 126 can operate at low power, in theorder of tens of micro watts, and provide a trigger output thatindicates motion has been detected. For example, the ultrasonicdetection module 126 can be implemented with a ultrasonic transmitterthat sets up a specific sound wave pattern that is received by anultrasonic receiver. Motion of objects in the field of the sound patterncan affect the received ultrasonic pattern by the receiver. Thesechanges can be detected by the ultrasonic receiver circuitry in theultrasonic receiver and this event can be used to activate the wirelesscamera 100 from a standby mode. Once activated, the wireless camera 100can initiate the various processing sections to start cycling and, forexample, start sending the surveillance data to the base station 160.

In another noise-level triggering mode the infrared detection module 124and/or the ultrasonic detection module 126 and the compression and/orcapture processing engine can continuously capture and store an on-goingwindow of surveillance data of the immediately previous seconds, minutesor hours. During this time the bulk high-bandwidth radio 104 can beinactive in order to save power. However, once motion is detected someor all of the previously stored information can be transmitted to thebase station or retrieved in other ways. This allows the activities thatoccurred in the area under surveillance prior to a trigger event to beinvestigated. In addition, other detection methods can be implemented ina manner similar to that described above for the infrared or ultrasonicdetection, but the triggering events can be initiated by other sensorsincluding magnetic sensors, relay or micro switches and window screenwired detectors.

The bulk high-bandwidth radio 104 can be a radio frequency and basebandchipset that implements the physical layer of the 802.11 standard. A keypurpose of this radio transceiver is to transfer the bulk of thecaptured and compressed surveillance data to the base station 160. TheMAC and other circuitry may or may not comply with 802.11 standards. Thechipset transceiver activities can be power cycled based on methodswhich will be discussed in further detail below.

Implementations of the techniques described here can be used to achieveefficient use of the high-bandwidth radio 104 in terms of energy per bitper unit of range (distance between transmitter and receiver)transferred. When active the radio can draw or dissipate relativelylarge amounts of power, however, due to the power cycling techniques,the power consumption of the wireless camera 100 can still besubstantially low. In particular, modulation techniques that use broadfrequency channels in the order of 5 MHz can be used. This is becausethese techniques exhibit low energy per bit (of data) per distance oftransmission. In one implementation, a multi-carrier modulationtechnique such as orthogonal frequency division modulation (OFDM) can beused. In another implementation, a spread spectrum modulation schemesuch as code division, multiple access (CDMA) can be used.

The low-bandwidth radio 106 can be, e.g., a low-overhead, long-rangeradio transceiver. The low-bandwidth radio 106 can be a radio frequencyand baseband chipset that implements any low power, low-bandwidthtechnique that will likely have longer reach and higher reliability thanthe bulk high-bandwidth radio 104. One purpose of the low-bandwidthradio 106 is to transfer status, control and alarm information to andfrom the base station 160. In receive mode, the power consumption can beextremely low in comparison to the bulk radio 104 and can be low enoughto allow the low-bandwidth radio 106 to operate continuously. Forexample, the power consumption can be in of the order of tens of microwatts.

Using this approach, the low-bandwidth radio 106 has a low power modewhere the radio 106 can be activated to respond to a short duration,beacon transmission that originates from the base station 160. The bitstream information contained in the beacon transmission can identify thecorrect camera and can also have other command/status information. Inanother implementation, the low-bandwidth radio 106 can be used as abackup when the bulk radio 104 fails or is disable, e.g., due to jammingsignals. In this manner, reliability of the wireless camera 100 can beincreased because there are a primary high-bandwidth radio 104 andsecondary low-bandwidth radio 106 for redundancy. In certainimplementations, the high-bandwidth radio 104 and the low-bandwidthradio 106 can be in the same transceiver block.

Additionally, errors in the bit stream of the beacon during transmissioncan be corrected by using forward error correction (FEC) techniques,such as hamming codes. Details of the forward error correction and itsassociated timing and phasing techniques will be described below. Thebit stream can serve as a “wake-up” function, allowing the base station160 to activate the correct wireless camera to wake-up and performcertain tasks during times when many components of the wireless cameramay be in the shut down mode. In one implementation, this low-bandwidthradio 106 can be achieved using “multi-standard” radio design, which mayshare portions or components used in the bulk radio 104. The sharing of“multi-standard” components can lead to lower cost or power from anoverall system perspective.

As noted above, the wireless camera 100 includes an internal battery102, which can be a standard non-rechargeable battery or a battery pack.In one implementation, a combination of rechargeable andnon-rechargeable batteries can be used. In another implementation, therechargeable battery can be replaced or augmented by so called supercapacitors. Such capacitors are readily available, e.g., from companieslike Maxwell Technologies Inc. The sources for the recharging energy caninclude, e.g., solar cells, fuel cells, galvanic cells, flow cells,kinetic power generators, and environmental energy sources. These energysources will be describe in more detail below.

The wireless camera 100 can make use of extensive active, highefficiency, power regulation and boaster circuitry to optimize the useof the energy available from various sources. Some or all of electronicprocessing and memory elements can be integrated into a single ASIC toreduce cost and power, creating a single chip wireless camera. Inaddition to the components shown in FIG. 1, a Pan, Tilt and Zoommechanism and control can also be included for user control of thewireless camera 100.

FIG. 2 shows a battery powered wireless network camera system 200 forvideo surveillance applications. In this example, the wireless networkcamera system 200 includes a wireless camera 210, a base station 220, awireless link 240 connecting the wireless camera 210 and the basestation 220, and a remote client 250. The system 200 can further includea network 260 connecting the base station 220 and the remote client 250.The network 260 can be a LAN or wide area network (WAN), a wirelessnetwork (e.g., WiFi, WiMax, or cellular networks), or power overethernet network (e.g., based on the IEEE 802.a3f standard). In otherimplementations, this network connection can be replaced by a universalserial bus (USB) interconnect directly connected to a computing device.From the client 250 or network 260 perspective, the wireless networkcamera system 200 can support extensive ethernet protocols including IP,HTTP, HTTPS, 802.1x, TCP, ICMP, UDP, SMTP, FTP, DHCP, UPnP™, Bonjour,ARP, DNS, DynDNS, and NTP. In particular, the base station code cancomply with well established IP camera API's from companies such as Axiscommunication's “VAPIX” API or similar API's.

A suitable wireless camera in FIG. 2 can be implemented in variousconfigurations, including the wireless camera 100 described in FIG. 1.The base station 220 can receive information (e.g., video and audioinformation) from the wireless camera 210 through the wireless link 240and process the received information. The base station 220 can also beone or more computers performing similar functions as a wireless basestation 220 and running a surveillance application. Hence, the computerscan function as the base station 220 and the client 250. For example,FIG. 3 shows another battery powered wireless network camera system 300for remote surveillance applications, where the surveillance client runson the same system as the base station 220, and the virtual web serverin the base station 220 can be eliminated.

Referring back to FIG. 2, the base station 220 includes a virtual webserver 222 for relaying or transmitting processed information to aremote client. The web server 222 can act as a virtual/proxy web cameraserver. Further, the web server 222 can shield the remote client 250(running a surveillance application) from the burst transmissionmechanism (which will be discussed in further detail below) of thewireless camera 210. In addition, the web server 222 can act as avirtual web server or relay server for a number of wireless cameras,aggregating the video streams but appearing to the surveillance remoteclient 250 as multiple separate virtual IP cameras. The web server 222can therefore transmit the camera data to the surveillance client 250using standard network means such as IP, HTTP, HTTPS, TCP, ICMP, UDP,SMTP, FTP, DHCP, UPnP™, Bonjour, ARP, DNS, DynDNS, 802.1x, and NTP.

As described above, by removing the web server for a network camerasystem out of the wireless camera 250, the wireless camera can achieveultra-low power consumption. However, unlike the wireless camera 210,the base station 220 requires a relatively robust external power supplyto allow for continuous operation of the web server 222. This powersupply can have a battery back-up to enable operation for periods ofhours to days during main power loss. It may also be possible to powerthe base station 220 from a large battery which is charged by arelatively large solar cell panel. In another implementation, the basestation 220 can obtain some or all of its power through a power overEthernet (POE) methods, such as the IEEE 802.3af standard. In this casealso the unit may have battery back-up capabilities.

Furthermore, the base station 220 can be a self-contained unit with nokeyboard or monitor to enable a small form factor. For example, the basestation 220 can have a form factor similar to that of a “wall wart,”which is a small power-supply brick with integral male plug, designed toplug directly into a wall outlet. Additionally, the wallwart style basestation 220 can use the Power over Ethernet methods for communicationswith the client device. In this manner, the base station 220 can be easyto install because it can be readily plugged in to a power socket. Thebase station 220 can also use flash memory or rotation media to storecaptured data.

As noted above, audio/video data can be requested by the clientapplication system through the network 260 and serviced by a virtual webserver 222 in the base station 220. Typically, the remote client 250consists of computer running a software application that analyzes and/orstores data for security and surveillance purposes. Multiple cameras canbe connected to a base station 220 via the wireless link 240. The clientcomputer can in turn run a surveillance application to access theconnected cameras. The client application can query the virtual webserver 222 in the base station 220 using standard or de-facto APIs suchas those available from Axis communications. In particular, the basestation code can comply with well established IP camera API's fromcompanies such as Axis communication's “VAPIX” API or similar APIs.

In one implementation, the base station 220 can be connected to theInternet through a cable modem or a DSL modem. In this manner, the IPaddress of the cable modem or DSL modem can be dynamically assigned. Theconstant changing of the IP address can make it more complicated tobuild a virtual web server on the base station 220 and provideaccessibility to clients on the Internet. A dynamic domain name server(DDNS) service can be used to allow users anywhere on the Internet to“find” the base station web server 222, even if its IP address isconstantly changing. A DDNS function can be provided to enable a fixedname for the web server so that remote users on the Internet can findthe IP address of the web server.

In certain implementations, the base station 220 can include softwarethat determines the dynamically changing IP address and forwards a newIP address to the DDNS. This can occur every time a new IP address isassigned by the local Internet Service Provider (ISP). The software cansend the necessary updates to all of the DDNS host names that need it.The user or remote client software can use a specifically constructed“domain name” and this would be setup in the DDNS hosting site.Therefore, if the IP address is changed by the local ISP then the DDNSupdates the DNS records and sets the TTL (time to live) to a value thatwill cause a propagation of the updated DNS record throughout theInternet. There are many common providers that provide hosting services,such as dyndns.org. Alternatively, domain names can be purchased or freeones can be obtained, but many of the free ones can have usagerestrictions.

Additionally, the remote client 250 can run on a handheld or wirelessdevice, such as a mobile phone, a personal digital assistance (PDA), asmartphone, or the like. In one implementation, the base station 220 caninclude image optimization processing software or hardware for relayingor transmitting the captured images to the remote client via a wirelessapplication protocol (WAP). For example, the base station 220 canperform image formatting, coding and communication in order to optimizethe image quality and behavior to the characteristics of the networklink and the constrained nature (bandwidth/size) of the handheld devicethat is running the client viewing software.

This image optimization processing can enable the base station 220 toonly send portions of the image at a time or only send zoomed-in imageinformation (to best fit to the smaller screen and lower networkbandwidth of the handheld device), or send images with lower resolutionor at lower frame rates. For example, this feature can allow an end userto remotely view the output of the wireless cameras from the convenienceof a handheld device, such as a mobile phone. Remote viewing of thewireless camera output from a handheld mobile device can be offered asan additional service to the user from the mobile network carriercompany (e.g., AT&T). This can create an attractive revenue generationopportunity for the mobile network carriers.

The base station 220 can also include a low-bandwidth, low-power radiobeacon 230 for communication with the wireless camera 210 via a secondwireless link. The secondary radio 230 can be low power, however, thetiming of this secondary radio 230 needs to be accurate in order to usethe bulk, high-bandwidth radio transmission efficiently. Thepredictability of the secondary radio coming on and transmittinginformation may need to be in the order of less than one millisecondresponse time in order to avoid wasting the channel time of thehigh-bandwidth bulk radio.

The wireless link 240 can include one or more wireless links. Forexample, a first wireless link can be a high-bandwidth wireless link anda second wireless link can be a low-bandwidth wireless link. Inaddition, the wireless link 240 can be an RF connection, a lowcomplexity LF, UHF or VHF connection with a baud rate of a few to tensof kilobits, a Bluetooth connection, a cellular network, a wirelessEthernet network, a WiFi network, or a WiMAX network. One example ofreceiver is the Texas Instrument's semi-passive RFID productTMS37122-TR. Another implementation for this type of radio can be seenin, e.g., “Low-power, super regenerative receiver targets 433-MHz ISMband”, as described in page 78 of the February-2006 issue of ElectronicDesign News. The network 260 connecting the base station 220 with theremote client 250 can be a wireless network (e.g., a Bluetoothconnection, a cellular network, a wireless Ethernet network, a WiFinetwork, or a WiMAX network) or a wired network (e.g., LAN/WAN network,or POE network).

Several power saving techniques can be used individually or incombination to reduce the overall battery energy consumption in thewireless camera. These techniques are listed and explained in furtherdetail below:

1. Move the camera web server to the base station and re-deploy it as avirtual web server.

2. Cycle the image/sensor bulk, high-bandwidth data transmission radiobased on the needs of the data rate and channel capacity.

3. Cycle the image capture module (hardware or software) based on themost efficient use of the module vs. latency, start-up/shut down timeand storage capacity needs.

4. Cycle the compression module (hardware or software) based on the mostefficient use of the module vs. latency, start-up/shut down time andstorage capacity needs.

5. Use of a secondary low-bandwidth radio with a longer range than thebulk radio for camera control and status report and triggering signals.

6. Activation of the camera functions based on various triggeringevents.

7. Use of environmental energy sources.

8. Use of pulsed high efficiency light emitting diode (LED) devices toilluminate the field of view.

Energy Saving Technique 1: Move the camera web server to the basestation and re-deploy it as a virtual web server.

One notable feature of the wireless camera described in thisspecification is that the wireless camera does not directly servicerequests for data received via a web server or a relay server mechanism.This is because there is no need for a web server to be running in thewireless camera. Instead, data transmission can be initiated andcontrolled by the burst transmission store/control block of the wirelesscamera. A substantial power saving can be achieved through thistechnique because it eliminates the need for web server functionality tobe present in the camera and allows the link radio to power down untilsensor and image data has to be transferred, not when the clientapplication needs data. (See power saving technique 2 below for furtherdiscussion.). However, through the use of the web server mechanism thecamera data can be available to client applications using standardnetwork means such as IP, HTTP, HTTPS, TCP, ICMP, UDP, SMTP, FTP, DHCP,UPnP™, Bonjour, ARP, DNS, DynDNS, 802.1X, and NTP.

Energy Saving Technique 2: Cycle the image/sensor data transmissionradio based on the needs of the data rate and channel capacity.

Technique 2 cycles a high-bandwidth radio bursting data on a periodicbasis determined by a burst period. Between the burst transmissions thehigh-bandwidth radio can be powered down. On average, the energy neededto transfer data can be optimized. In one implementation, an 802.11based physical layer technology can be used to transfer the bulk data.The physical layer technology used can include broadband high efficiencyOFDM modulation architectures. The OFDM modulation technique can exhibitlow energy per bit transferred per unit of range vs. other commonly usedradio link architectures, such as the 802.15.4 OOC/FSK modulationtechniques.

The wireless camera can include a high-bandwidth radio transceiver,which can operate under a steady state communication condition. Forexample, the wireless camera media access control (MAC) for thehigh-bandwidth radio can be programmed to setup/tear down connections asdetermined by the Transmission Store/Control Block. This allows thehigh-bandwidth bulk data transmission radio to power down completely forextended periods of time.

When the radio is switched on it can be instantly assumed to belogically linked with the base station. A primitive MAC layer can beused, but this may not be the preferred implementation. Thus, the radiocan avoid the usual discovery period, and advance to the authenticationrequest and reply, followed by the associated request and reply messagesin a three-way handshaking process. This differs from the regular beaconbehavior of 802.11 when operating in a rendezvous mode. Discoverysequences can be suppressed except during initialization/installationconditions. A very light OS can run on the wireless camera to bring upthe MAC with the minimal configuration. This can reduce the need for thepower and time consuming mechanisms associated with current wirelesslink technologies. In certain implementations, the MAC layer can almostbe entirely eliminated from the camera and a rudimentary slave responsecan be implemented which responds to control signals received from asecondary, low-power, low-bandwidth radio channel.

The algorithm for the burst transmission processing is a timing loopwhere data is transmitted based on the data rate used and the availablechannel characteristics. A calculation is done to determine the optimumtiming for the burst transmission and the system is then set up to matchthis as closely as possible. During non-transmission periods thehigh-bandwidth radio can be completely powered down. This can bedifferent from “doze” or “standby” modes often provided by commercialintegrated circuits. These modes often dissipate energy at levels thatcan defeat the possibility of extremely long term battery life. Duringthis non transmission time the high-bandwidth radio can use less thantens of micro watts of power.

The timing to transmit for the burst transmission is based on thefollowing parameters: Average Maximum Channel Bandwidth is representedby Bm in M bits per second (Mbps). Channel bandwidth is the averagebandwidth that can be achieved by the high-bandwidth link. Averagesustained Data Rate is represented by Bs in Mbps, which is the data rateof captured audio/video data. The higher the rate, the better thefidelity and frame rate of the transmitted information.

FIG. 4 is a diagram showing the burst data transmission, according tosome implementations. To take advantage of the fact that the sustaineddata rate Bs is much smaller than the capability of the bulk radio; thetransmission will be on for a brief period of time to burst the data.This period can be designated by Tx (sec), and the time period betweenbursts can be represented by Tc (sec).

Hence

Tx·Bm

Tc=Bs

Referring to the bottom of FIG. 4, there can be a time associated withsetting up the link and terminating the link. For example, the time toset up link is represented by Tsu (see), and the time to tear down linkis represented by Ttd (sec). Therefore the aggregate time to set-up andtear down link Tw=Tsu+Ttd (sec). To obtain maximum power savingefficiency on the bulk, high-bandwidth radio, ideally the ratio of thetransmit time Tx to power down time should be equal to the ratio betweenBs and Bm.

During the Tx period, the power drawn by the high-bandwidth radio can bevery high relative to the power down periods. For example, the wirelesscamera in the 802.1 in transmitter which is operating using diversity ormultiple transmitters can use between 100 mW to 1.5 W during the Txperiod instead of a few hundred microwatts in other periods. This levelof power consumption during the transmission of data can be adistinguishing feature of this system compared to existing low powerremote sensor systems.

In the image transmission operation, various battery operated camerasystems which transmit data intermittently, can have a transmitter-offto transmitter-on ratio of 10 or less. As such, the transmitter in thesewireless camera systems is on most of the time. In contrast, of thetransmitter in the present systems can be designed to have ahigh-bandwidth radio for transmission and such a high-bandwidth-ratiotransmitter is on only for a short period of time. In this manner, theburst transmission of the current wireless cameras systems can have atransmitter-off to transmitter-on ratio of much greater than 10 and thusprovide significant saving in power consumption.

However, the system timing needs to take into account the “wasted” timenecessary to setup and tear down the link during which the radio isactive, which is Tw. In order to approach the ideal efficiency, periodTw needs to be amortized across a relatively long period of active datatransmission time (Tx). This means that the time in-between bursting theradio, as represented by Tc, can be extended as Tw increases to maintainthe same efficiency level. Hence the efficiency (E, in percentage) canbe determined by

$E = {{\frac{Tx}{( {{Tx} + {Tw}} )} \cdot 100}\%}$

Given the above, the average optimum time between transmission of theburst of audio/video (Tc) data for a given efficiency E, can bedetermined as follows:

${Tc} = {\frac{Bm}{Bs} \cdot {Tw} \cdot \frac{E}{E( {1 - E} )}}$

The following example can better illustrate the equation above:

Tw=3 ms (highly optimized system)

Bin=54 M bits/sec (ideal 802.11g data rate)

Bs=192 k bits/sec (5 frames/sec with 0.5 bits/pixel at 320×240, noaudio)

E=75%

Then the best cycle time to set-up and burst transmission is, Tc=2.53seconds.

System latency (or lag) can be greater than or equal to Tc. If latencyis too high an unacceptable lag can occur between the capturing ofaudio/video information to its availability to serve a surveillanceapplication. To reduce latency without negatively impacting energyconsumption, significant optimizations need be made to the MAC behaviorin order to reduce Tw. In order to reduce time period Tw during steadystate conditions (i.e. not during discovery or initialization states)certain modifications can be made. For example, a modification to theregular beacon behavior of 802.11 can be made. When the high-bandwidthradio is switched on for transmission, it can be assumed to besynchronized with the base station. Thus, the usual discovery period canbe avoided and the high-bandwidth radio can advance immediately to theauthentication request and reply, followed by the associated request andreply messages. Further, when the high-bandwidth radio is switched on,communication can be made for data transfer only.

The above scheme can be implemented to provide a significant improvementbecause the wireless camera communication can operate on a time framedetermined by the need to transmit data of interest, and not on a timeframe determined by the client surveillance software application. Also,when multiple cameras are connected to the network using this method,the transmission burst cycle for each camera can be set so as not tointerfere which each other. For example, this can be done atinitialization time by the burst reception store/control processingmodule of the base station.

In one implementation, a timestamp can be inserted in the capturedimages based on the time that the images were captured by the wirelessvideo camera. In this manner, any latency between the time of datacapture and the time of viewing or manipulating the images at the clientdevice can be accommodated. For example, suppose that a series of imageswere captured at 12:00 a.m., however, due to a temporary failure ordelay in the transmission the client device does not receive the imagesuntil 12:10 a.m. The inserted timestamps in the captured images can beused as the reference point for image processing or manipulation. Theinsertion of the timestamps can occur at the camera or at the basestation.

The base station's high-bandwidth radio MAC firmware can take advantageof “knowing” for long extended periods of time what specific wirelesscamera radios are associated with it. This can allow set-up and teardown of connections without discovery sequences, by only requiringconnection via authentication request and reply followed by theassociated request and reply messages. The base station can beimplemented in various configurations. In one implementation, a basestation implementing standard 802.11 protocols can be used by thesystem.

Non Clear Channel Environments

In a non-clear channel environment (e.g., during interference from othertransmitters which may be using the channel) the high-bandwidth radiotransmission period can be “skipped” and the data that was to betransmitted can be temporarily stored and transmitted on the nextavailable cycle. In these conditions, the period and timing oftransmission bursts can vary based on channel conditions.

For example, in one implementation, the camera can include a separatelow power circuitry to determine if a high-bandwidth radio transmissionchannel is open or not prior to a transmission cycle. This informationcan be used to determine if the high-bandwidth radio in the camera isactivated from a power down mode or that transmission period is“skipped” by the camera. Using standard 802.11 MAC protocol, if thechannel is open the camera can initiate the transmission process bysending a Request to Send (RTS) frame. The base station can then replywith a Clear To Send (CTS) frame. As specified by the standard, anyother node receiving the CTS frame should refrain from sending data fora given time.

FIG. 5A shows a flow chart of a MAC algorithm 500 that can be used bythe wireless camera. At 505, the wireless camera is initialized, e.g.,by going through a discovery mode. At 510, the wireless camera scans forthe base station. At 515, the system configures the wireless camera tosynchronize with the base station. Once the wireless camera has beeninitialized and synchronized with a base station, the camera can thenenter a power down or standby mode, at 520, when the camera is inactive.On the other hand, based on a triggering event as described above, at530, the camera can be powered on and enter active mode.

Once the camera is powered on, at 535, the camera transmits an RTS frameto the base station. If a channel is available, the base station canthen reply with a CTS frame. At 540, the system determines whether a CTSframe is received from the base station. If the CTS frame is received,at 565, the camera starts to transmit captured or stored image data. Onthe other hand, if the CTS is not received from the base station, at560, the camera stores the captured data in the storage device, andperiodically transmits an RTS frame to the base station.

In addition, once the RTS frame has been received by the base station,the base station scans for available channels, at 545. At 550, the basestation determines whether there are available channels to establishconnection with the wireless camera. If there is an available channel,at 555, the base station reserves the channel and then sends a CTS frameto the camera. On the other hand, if there is no available channel, thebase station keeps scanning for available channels.

In another implementation, the base station can include processingcircuitries or operating modes that can determine if a high-bandwidthradio transmission channel is open or not on a regular basis. Thischannel availability information can be transferred to the camera usingthe secondary low-bandwidth radio connection. One benefit of providingthis processing on the base station can be a significant power reductionin the camera, since the processing does not occur using the camera'spower. Also, the incorporation of the channel availability processingcircuitry or operating mode in the base station can allow for complexand power-intensive processing to be executed for system operation.

The base station can then emulate a standard 802.11 CTS/RTS handshakingoperation. In this manner, both the primary and the secondary radios ofthe base station can be used to establish handshaking. Here the basestation itself generates the RTS signal which would normally be expectedfrom the camera. This RTS signal can cause surrounding nodes to stay offthe channel. This can also eliminate the need for the camera to generatethe RTS signal and allow the camera to shut down between time periods ofactual data transmission. As noted above, the camera can be activated bythe secondary radio operation to transmit more data, or from an internaltimer. The whole sequence of emulated CTS/RTS handshakes of datatransmission can be pre-determined.

In one further implementation, if a high-bandwidth radio transmissionchannel is open, the base station can reserve and hold the channel. Itcan do this by using standard 802.11 MAC channel accessing techniques.During this sequence, the base station can signal the camera using thesecond wireless link that the bulk channel is open. The base station canthen immediately stop transmitting and can “release” the channel. Thetiming can be configured so that the high-bandwidth radio in the cameracan then be activated from a power down and transmission begins suchthat, from an external observing radio, the channel was never releasedfor any material length of time.

Additionally, the above method of “reserving” and “holding” of thechannel for a period of time can be implemented in the base stationusing the “CTS-to-self” signaling method in the 802.11 standard. Thisway, an association between the base station and the camera can beestablished prior to the base station entering the CTS/self mode. FIG.5B is a flow chart showing a process 500B that can be used to implementthe CTS-to-Self algorithm. Initially, at 570, the base station scans foravailable bulk, high-bandwidth radio channels. At 572, the base stationdetermines whether the bulk, high-bandwidth radio channel is available.If the bulk radio channel is available, at 574, the base station sends aCTS/Self signal to reserve the available channel. In this manner, theCTS/Self signaling technique available in the 802.11 standard can beused to keep surrounding 802.11 nodes quiet for a period of time,thereby reserving the available channel. On the other hand, if the bulkradio channel is not available, process 500B iterates at 570 and thebase station continues to scan for available channels.

Once the channel has been successful reserved by the base station, at576, the base station can then send rapidly, with low latency, aproprietary “wake-up/CTS” signal (somewhat similar to the CTS signal) tothe camera via the secondary or low-power radio channel. This differsfrom existing 802.11 MAC procedures where the CTS information is sentonce through the primary (or bulk) radio on the camera. At 578, thecamera receives the CTS signal from the base station using the secondary(low-power) radio on the camera. The secondary radio on the camera, at580, then rapidly trigger a “wake-up” signal to the primary bulktransmission radio in the knowledge that the bulk (primary) transmissionchannel has been reserved and should be clear. At 582, the cameratransmits the image data to the base station via bulk transmissionchannel reserved by the base station. At 584, this image data isreceived by the base station via the high-bandwidth channel.

One advantage of using the above CTS-to-self signaling technique is thatthe bulk transmission (primary) channel can be held open according to802.11 standards for a relatively long period of time. This period canbe relatively long to allow for backward compatibility with much older(slower) bandwidth modulation schemes such as 1 Mbit/sec. In thestandard, the time reserved by a CTS-to-self can be determined by theduration field in the CTS frame. In this method, the CTS is sent by thebase station with usual contention period rules (i.e. after the DIFSquiet air time), and it can be honored by any device close enough tocorrectly demodulate it.

The above described methods, that of having the base station do the workof reserving the channel and only alerting the camera when the channelis known to be clear and signaling this through the low-power secondaryradio, can significantly lower the overall power requirement in thecamera. This is because the camera does not have to power up a powerhungry bulk transmission receiver radio to determine if the channel isclear. Instead, the camera powers up the high-bandwidth transmitter whenthe channel is likely to be clear of other WiFi compatible nodes in thenetwork.

In addition, the secondary (low-power and low-bandwidth) radio canimplement a hierarchy of up-power modes to provide sustained ultra lowpower operation. For example, a “carrier sense” mode can be availablewhere only the front-end section of the radio is powered-up to detect ifa carrier of a certain narrowband frequency is present. This carriersense mode can be designed to be extremely low power and can beoperational for extended periods of time. In this method of operation,if the front-end section of the secondary radio detects a likely carriersignal, then further demodulation can be triggered to search for aspecific leading signature bit sequence. This sequence can be used todetermine if the signal is a valid transmission from the base station.If the sequence is valid, then further bits are decoded, if not then thesecondary radio can revert back to the low power carrier sense mode.

The method described above, i.e., that of using a low-power secondaryradio to receive control, to “wake-up” and to receive other informationabout the status of a primary high-bandwidth transmission channel isdifferent from various wireless schemes in other wireless camerasystems. For example, one of the differences between the presenttechnique and others is using one modulation scheme for the transmissionof control information and a different modulation scheme for thetransmission of data (e.g., captured image data) information. This canallow the receiver to be low-bandwidth and be design to consume very lowpower. Another difference from existing wireless schemes can be that thedemodulation and/or carrier detection of the secondary radio can be onfor extended periods of time in order to listen for the secondarychannel and/or demodulate the control/status information.

Furthermore, operational benefits can be achieved by having thesecondary radio on at all times when compared to a secondary radio thatuses polling (i.e. comes on at intervals to poll for a transmission).For example, this can reduce the need to have timing synchronizationwith a base station, and can make the system design simpler and morerobust. In addition, this can reduce primary channel (high-bandwidthchannel) airtime consumption. The is because a polled secondary radiocan, on average, add half the polling interval time to the time neededby the camera to transmit the video images on the primary channel. Thisadditional airtime consumption can impact the overall efficiency of theprimary channel. This can affect other nodes sharing the channel in asignificant way by reducing their overall throughput. With carefuldesign techniques, this constantly on secondary radio can consume poweron average in the order of under 1 mW in power during extendedoperation. This can further allow the secondary radio to be availablefor many months to years using the energy from a small battery or afraction of the energy from a larger battery pack.

Legacy Compatibility Advantages

A further benefit of the above approaches to implementing 802.11 MACcompliant protocol processing (but in a novel way using the secondaryradio) is that the arrangement is a “good citizen” in a WiFi compatibleenvironment and will behave well with legacy standard 802.11a/b/g nodes.This can allow the deployment to be widespread and by not affectingnormal operation of any legacy compatible network. In the above methodsthe latency to “wake-up” the camera through the secondary radio andset-up the link after this trigger can be designed to be as low aspossible and is the same parameter as described above as Tsu. Theaccuracy of the secondary radio to wake up external circuitry may needto be predictable and should ideally in the order of microseconds toavoid wasting bandwidth on the primary (bulk) channel.

Newer 802.11e Systems with QoS Schemes

In another implementation, the transmission cycles can adhere tostandardized system wide quality of service (QoS) schemes, such as thatof the IEEE 802.11e standard. The base station can implement a PointCoordination Function (PCF) between these beacon frames. The PCF definestwo periods: the Contention Free Period (CFP) and the Contention Period(CP). In CP, the DCF is simply used. In CFP, the base station can send aContention Free-Poll (CF-Poll) to each camera via the primary (bulk)) orsecondary radio, one at a time, to give the camera the permission tosend a packet.

In another implementation, the IEEE 802.11e standard using the HybridCoordination Function (HCF) can be used. Within the HCF, there are twomethods of channel access, similar to those defined in the legacy 802.11MAC: HCF Controlled Channel Access (HCCA) and Enhanced DistributedChannel Access (EDCA). Both EDCA and HCCA define Traffic Classes (TC).The captured data transmission can be assigned a high priority usingthis scheme. Using the EDCA method, the base station can assign aspecific Transmit Opportunity (TXOP) to a specific camera. A TXOP is abounded time interval during which a specific camera can send as long asit is within the duration of the pre-assigned TXOP value. Additionally,Wi-Fi Multimedia (WMM) certified nodes need to be enabled for EDCA andTXOP.

Alternatively, the system can also use the HCCA scheme to allow for CFPsbeing initiated at almost anytime during a CP. This kind of CFP iscalled a Controlled Access Phase (CAP) in 802.11e. A CAP is initiated bythe base station, whenever it wants to send a frame to a remote node, orreceive a frame from a node, in a contention free manner. In fact, theCFP is a CAP too. During a CAP, the base station, which can act as theHybrid Coordinator (HC), controls the access to the medium. During theCP, all stations function in EDCA. The other difference with the PCF isthat Traffic Class (TC) and Traffic Streams (TS) are defined. This meansthat the base station (implementing the HC function) is not limited toper-camera queuing and can provide a kind of per-session service.

Furthermore, the HC can coordinate these streams or sessions in anyfashion it chooses (e.g., not just round-robin). Moreover, the stationsgive information about the lengths of their queues for each TrafficClass (TC). The HC can use this information to give priority to onestation over another, or better adjust its scheduling mechanism based onthe captured data burst transmission needs as described above. Anotherdifference is that cameras are given a TXOP: they may send multiplepackets in a row, for a given time period selected by the HC. During theCP, the HC allows stations to send data by sending CF-Poll frames. Withthe HCCA, QoS can be configured with great precision. QoS-enabledcameras can have the ability to request specific transmission parametersand timing as determined by the burst transmission needs describedabove.

Energy Saving Technique 3: Cycle the image capture module (hardware orsoftware) based on the most efficient use of the module vs. latency,start-up/shut down time, frame rate and storage capacity needs.

For example, in a possible power saving method, after the exposureprocess, the pixel read out for the image captured from the sensor mayoccur at the maximum clock output rates allowed by the sensor. This ratemay be many times the sustained data rate. This allows the sensor andassociated circuitry to power down for significant periods between frameexposures. The image capture engine/processing sections of the cameracan also power up and down on a periodic basis independent of othersections of the camera. When operating in the capture mode, uncompressedimage can be loaded into an SRAM memory, which temporarily holds thedata until it can be processed by the other main sections of the camera.When operating in the power-down mode this section can retain the datain SRAM or some other memory in a low power standby mode.

This cycling can allow the image capturing module to operateindependently of other sections. Therefore, each section can cycle on aperiodic basis most efficiently to save energy with respect to latency,start-up/shut down time, and storage capacity needs. Further, thiscycling technique can offer power savings over that of a simple powerdown mode where the whole camera except for a “wake-up” section ispowered down.

Energy Saving Technique 4: Cycle the compression module (hardware orsoftware) based on the most efficient use of the module vs. latency,start-up/shut down time and storage capacity needs.

The image compression engine/processing sections of the camera can alsopower up and down on a periodic basis independent of other sections ofthe camera. When operating in the capture mode, compressed image isloaded into an SRAM memory, which temporarily holds the data until itcan be processed by the other main sections of the camera. Whenoperating in the power-down mode this section can retain the data inSRAM or other memory in a low power standby mode.

This cycling can allow the compression module to operate independentlyof other sections. Therefore each section can cycle on a periodic basismost efficiently to save energy with respect to latency, start-up/shutdown time and storage capacity needs. Further, this cycling techniquecan offer power savings over that of a simple power down mode where thewhole camera except for a “wake-up” section is powered down.

The image compression algorithm in the wireless camera does not need tobe the same as the compression algorithm used in the base station forsending image information to the client application. For example, anon-standard, proprietary compression algorithm, which can be cheaperand/or consume lower power, can be used on the camera. The compresseddata from the camera can be transcoded to a well-know standard (e.g., aJPEG standard) by the base station; and therefore, the proprietary imagecompression algorithm of the camera can be “transparent” to the clientapplications. Alternatively, the compressed data can be transmitteddirectly to the client without transcoding by the base station, if theclient can process the compressed data from the camera.

Energy Saving Technique 5: Use of a low-bandwidth transceiver with alonger range than the high-bandwidth data transmission transceiver forcamera control and status report.

Low-bandwidth, low power transceivers can be expected to draw onlymicrowatts of power in receive mode. The modulation techniques andfrequency band of the low-bandwidth radio can be different from thehigh-bandwidth data transmission radio. As noted above, thehigh-bandwidth and the low-bandwidth radios can be integrated togetherinto a single transceiver block having dual radios.

The function of the low-bandwidth radio can be for side bandcommunication without having to power up the high-bandwidth radio. Itcan allow the camera to be “listening” for instructions during deepsleep mode configurations without needing relatively large power drain.The specifications of the low-bandwidth radio can have longer range butmuch lower bandwidth than the high-bandwidth radio. Thus, undersituations where the high-bandwidth radio cannot establish a link withthe base station, the low-bandwidth radio can operate as a back-up radioand effectively communicate with the base station.

The low-bandwidth radio can further reduce its “listening” energyconsumption by operating in a polling mode. In the polling mode, theradio section of the low-bandwidth radio can cycle from active tostandby. During the active mode, the low-bandwidth radio listens forburst transmission from the base station, captures the data and thengoes back to stand-by. In one implementation, this cycle timinginformation can be accurately known and determined by the base station.

Furthermore, the low-bandwidth radio can be used to receivePan/Tilt/Zoom (PTZ) information and other commands. These other commandscan be triggering operations such as transmission, capture andcompression or shut down for long periods of time. The low-bandwidthradio can further be used to send status information to the basestations regarding the health of various components on the wirelesscamera (e.g., the high-bandwidth radio). Because the low-bandwidth radiocan have lower latency than the high-bandwidth radio, the low-bandwidthradio can be used for two way audio communications.

Energy Saving Technique 6: Activation of the camera functions based onvarious triggering events.

As described above, the camera operation can be triggered by one or moreexternal conditions such as availability of light, motion sensing,passive infrared (PIR) detector, sound or time of day, week or month. Inone implementation, the triggering event can occur through theprocessing of the captured image data.

Energy Saving Technique 7: Use of environmental energy sources. Asdescribed in more detail above, various environmental energy sources,such as solar cells, fUel cells, kinetic power generators and otherenvironmental energy sources can be used to power the camera.

Since the average power consumption of the wireless camera can berelatively small, a solar cell or solar cell array can be used as apower source for the camera. This solar cell or solar cell array can beused to recharge a battery or a high capacity capacitor which can powerthe camera during night time or low light conditions. Further, since thesolar cell can be small, it can be attached to a side of the housing ofthe wireless camera. A suction cap (e.g., a vacuum, push-on sucker) canbe mounted on the solar panel side of the housing. This can allow thecamera to be quickly mounted on the inside surface of a window pane of abuilding or a vehicle, such that the solar cell faces the outside tocapture light energy, while the imager lenses conveniently faces insideor outside the vehicle or building to capture images.

Additionally, the entire wireless camera can be recharged on a chargingstation or can have interchangeable battery packs that can fit into acharging station. For example, the interchangeable battery packs can besimilar to the batteries used for cordless phones or mobile phones. Theinterchangeable battery pack can also use non-rechargeable batteries.Furthermore, the wireless camera can be adhered to a surface with amounting mechanism. This mounting mechanism can be separate from thewireless camera. This mounting will have means that allow the cameras toattached to the mounting quickly and easily while keeping camera's fieldof view constant. In another embodiment the camera may be mounted on awindow pane using suction-cups.

In one implementation where a solar cell is used to charge arechargeable battery during hours of light, there can be wear-out of therechargeable battery. Typically re-chargeable cells can have a limitednumber of charge, recharge cycles. For example, if the rechargeable cellis good for 365 cycles, the cell can only be usable for approximatelyone year of day/night recycles, thus limiting the camera life toapproximately one year. To avoid this problem, an array of cells can beused by the camera. By selecting from a limited set of cells inside thearray that will be used for a given number of cycles, thecharge/discharge cycle burden can be distributed over the array.

In one implementation, an array of 12 rechargeable battery cells can beused. The 12 cells can be grouped in groups of three battery cells. Onegroup of three cells can be selected for a 12 month operation of chargeand recharge cycles. After 12 months, the next group of three cells canbe used, and during the third year the next set of three cells can beused and so on. In this way, overall usable lifetime of the rechargeablebattery cell array can significantly exceed that of a single cell.Alternatively, the division of the charge/recharge cycle burden can beachieved by a specialized circuitry that alternates charging betweencells or cell groups and on a varying timing cycle other than the 12month cycle as described above.

During the transmission periods of the high-bandwidth radio, the energyconsumption can be significant. Drawing a high current from a smallbattery cell directly connected to the camera power input can causeaccelerated wear out of the battery. Therefore, a high efficiencycircuit can be used to avoid the wear out of the battery by limiting themaximum current draw from the battery. FIG. 6 shows a block diagram of abattery current limiting circuit that can be used to connect to thecamera power input. Other implementation can use alternative energysources (instead of the battery) such as solar cells, galvanic cells,fUel cells, kinetic power generators, or other environmental sources.The battery current limiting circuit can also help maintain efficientoperation in these types of alternative energy sources.

As shown in FIG. 6, a regulator 600 is used to control the maximumamount of current drawn from a battery 602 (or alternative energy sourceas described above). This regulated current draw is then used to chargea holding capacitor sub-circuit 610. This sub-circuit can be acapacitor, a super capacitor, or other high reliability charge holdingdevice capable of handling current surges better than the battery (oralternative source). The current regulator 600 can include a switchedregulator 604 (e.g., a buck regulator) or other active type regulator tomaximize efficiency in charging the holding capacitor 610. A currentsensor feedback loop can be implemented to monitor the current appliedto the holding capacitor 610. For example, one monitoring circuitry canbe achieved by amplifying the voltage across a low value sense resistorconnected in series with the supply current.

Additionally, a second regulator can be used as a voltage regulator tosupply a controlled voltage source to the camera power input. Thisvoltage regulator can be implemented as a switched regulator 612 (e.g.,a buck regulator), or other active regulator to maximize efficiency insupplying a voltage source to the camera input. In one implementation,the power regulation circuit can have the ability to adjust the level ofcurrent drawn from the energy source under programming control. Forexample, this can be achieved by adjusting the gain in a sense feedbackloop or the set-point in the feedback voltage. This capability can allowfor a variety of alternative energy sources (or modes of operation ofthose sources) to be used.

To make the wireless camera easy to use, the camera can have the certainswitches/settings available to the user. For example the camera caninclude features for operation in darkness (on/off), operation based onsound detection, operation based on infrared detection, and operationbased on other triggers. The camera can further include an option forthe user to choose the duration of operation (time period the cameraneeds to operate, e.g., 3 months, 6 months, 1 year or other similardurations). Software can be used to calculate frame rate that need to beused so that the batteries can last for the indicated time.

During set-up mode the camera's wireless link can be powered upcontinuously (not cycling) for an extended period of time to enable, forexample camera focus and field of view set-up to be configured simplyand easily. In applications where system latency may cause the period Tcto become unacceptable, the signaling to the low-bandwidth radio can beused to trigger faster cycling and reduce Tc. However, this can reduceenergy efficiency. Also, to make the base station easier to install, itcan be powered through the Ethernet cable using power over Ethernet byimplementing the IEEE802.3af standard or similar methods.

The characteristics of standard 802.11 wireless links can often lead tounreliable or inconsistent connectivity. This is usually due tointerference or other environmental factors. This can make set-up and/oroperation erratic. These issues can be addressed through the followingmethods:

a) The media access techniques used by the system need not be the sameas the MAC standards of 802.11. Therefore, in poor connection conditionsspecific and more restrictive channel access techniques can be used byignoring other radios and forcing and holding a connection. If thesecondary low-bandwidth radio is implemented in the camera, thesetechniques can be triggered and controlled through the secondary radiosince it can establish a link in conditions where the high-bandwidthradio cannot. For example, the base station can include circuitry thatdetermines if a channel is available for the primary radio (bulkhigh-bandwidth radio).

b) Since the base station has information about the transmissionbehavior and expected state of the camera, it can detect and correctlink problems by requesting retransmission of the data. This request canbe sent via the secondary low-bandwidth radio which can be more reliablethan the high-bandwidth channel. This retransmission can be hidden andtransparent to the client surveillance application through the virtualweb server in the base station.

c) A highly asymmetrical radio link can be implemented for thehigh-bandwidth radio where the antennae and processing in the basestation uses high gain techniques such as multi antenna (MIMO) and highsensitivity RF front-end processing to help reliably capture thetransmission data from the camera.

Energy Saving Technique 8: Use of pulsed high efficiency light emittingdiode (LED) devices to illuminate the field of view

In applications where there is little light, or light has been disruptedby a disaster or a failure condition (e.g., an electrical failure), thecamera may operate in the dark and the image sensor may not captureuseful data. In conventional camera systems, this situation is addressedby attaching an auxiliary light source near or on the camera. Lightsources operating continually to illuminate an observation area duringvideo surveillance can consume significant energy. In oneimplementation, the wireless camera system described in thisspecification can save energy by pulsing a high efficient infrared orvisible light LED, synchronized to the image capture frequency andphase. The operational duration of this scene illumination light pulsefrom the LED can be minimized by a careful calculation of thesensitivity and exposure time needed by the image sensor to successfullycapture images. In addition, scene illumination using the LED devicesneed be implemented only when necessary to capture an image, and overallenergy consumption of the camera can be reduced.

Camera Shutdown and Privacy Enhancements

In applications where users would like to shut down (or deactivate)certain cameras, various enhancements can be used. In oneimplementation, for example, all or some camera may need to be shut downin situations where recording is not needed or is preferred to bedeactivated. This can include situations where an authorized resident ispresent such as inside the residence or premises. Another example can bea camera installation in a locker room or changing room for use whenthese facilities are expected to be empty. This can be due to privacyreasons, or simply that the system operator would prefer certain camerasto be off.

In the deactivated (i.e., non-recording) mode, the secondary,low-bandwidth radio can still be on, giving the camera the ability to bereactivated when necessary. Furthermore, this ability to shut down thecamera except for the operation of the low power secondary radio, canalso allow for longer batter life. Therefore, each camera can beindividually deactivated based on control information received via theprimary or secondary radio link.

The camera activation or deactivation can also be manually set by anoperator, or be linked to an existing alarm system or to a pre-settiming cycle. Deactivation can be overridden under certain circumstanceseither automatically (such as an alarm trigger), or manually (locally orremotely). Activation periods of the wireless cameras can be manuallyoverridden. In addition, these periods of override can themselves betimed to last a specific period of time, for example minutes or hours.Furthermore, for ease of use and convenience reasons, the setting,initiating and overriding of the modes of activation/deactivation ofcameras can be operated from a hand-held remote control.

A visual indication can be made available on the camera usingintermittent flashing LED. For example, a red LED can be used toindicate that the camera is in active recording operation. However, someobservers or personnel in the camera's field of view may not believethat the camera image recording or viewing capability is truly “off”. Inone implementation, to address this concern, the camera can have amechanically operated, privacy lens cap or an easy-to-observe, visibleshutter that obscures the camera lens in an obvious way to make it clearto the observer that the camera cannot be recording or capturing images.

For example, the material of the privacy lens cap can be an opaquematerial such as a solid sliding window that covers the entire front ofthe lens surface. To make the fact that the lens is obscured very clearto any observer, the privacy lens cap or visible shutter should bevisually clear. For example, if the casing of the camera is white, andsince the lens of the camera appears block, the privacy lens cap can bean opaque material such as a solid white sliding window. This way, anobserver will not see the darkness of the lens iris or any dark holes onthe camera that might indicate an image capturing capability.

A further mechanism to obscure the lens and achieve privacy enhancementcan be implemented by causing the lens to retract or roll back into thecamera case in such a manner that the lens is no longer pointing intothe observation area. For example, in a Pan/Tilt/Zoom (PTZ) type camerathis can be implemented by altering the design of the camera to extendthe rotational range of the PTZ mechanism beyond the usually implementedrange. Therefore, when privacy enhancement is initiated in such analtered PTZ type camera, the visual confirmation to an observer can besomewhat akin to an “eyeball rolling back in its socket”.

This mechanical privacy lens cap, shutter or mechanism can be activatedor deactivated automatically or manually, and locally or remotely. Forexample, in some implementations, the user can manually (e.g., usingtheir hands on the camera) initiate activation (closing or obscuring thelens) and deactivation (opening or making the lens visible) of theprivacy lens cap or shutter. Furthermore, this privacy lens cap orshutter system can be used on both wired and wireless cameras forprivacy enhancement purposes.

FIG. 7 is a block diagram of computing devices and systems 700, 750.Computing device 700 is intended to represent various forms of digitalcomputers, such as laptops, desktops, workstations, personal digitalassistants, servers, blade servers, mainframes, and other appropriatecomputers. Computing device 750 is intended to represent various formsof mobile devices, such as personal digital assistants, cellulartelephones, smartphones, and other similar computing devices. Thecomponents shown here, their connections and relationships, and theirfunctions, are meant to be exemplary only, and are not meant to limitimplementations of the inventions described and/or claimed in thisdocument.

Computing device 700 includes a processor 702, memory 704, a storagedevice 706, a high-speed interface 708 connecting to memory 704 andhigh-speed expansion ports 710, and a low speed interface 712 connectingto low speed bus 714 and storage device 706. Each of the components 702,704, 706, 708, 710, and 712, are interconnected using various busses,and may be mounted on a common motherboard or in other manners asappropriate. The processor 702 can process instructions for executionwithin the computing device 700, including instructions stored in thememory 704 or on the storage device 706 to display graphical informationfor a GUI on an external input/output device, such as display 716coupled to high speed interface 708. In other implementations, multipleprocessors and/or multiple buses may be used, as appropriate, along withmultiple memories and types of memory. Also, multiple computing devices700 may be connected, with each device providing portions of thenecessary operations (e.g., as a server bank, a group of blade servers,or a multi-processor system).

The memory 704 stores information within the computing device 700. Inone implementation, the memory 704 is a computer-readable medium. In oneimplementation, the memory 704 is a volatile memory unit or units. Inanother implementation, the memory 704 is a non-volatile memory unit orunits.

The storage device 706 is capable of providing mass storage for thecomputing device 700. In one implementation, the storage device 706 is acomputer-readable medium. In various different implementations, thestorage device 706 may be a floppy disk device, a hard disk device, anoptical disk device, or a tape device, a flash memory or other similarsolid state memory device, or an array of devices, including devices ina storage area network or other configurations. In one implementation, acomputer program product is tangibly embodied in an information carrier.The computer program product contains instructions that, when executed,perform one or more methods, such as those described above. Theinformation carrier is a computer- or machine-readable medium, such asthe memory 704, the storage device 706, memory on processor 702, or apropagated signal.

The high speed controller 708 manages bandwidth-intensive operations forthe computing device 700, while the low speed controller 712 manageslower bandwidth-intensive operations. Such allocation of duties isexemplary only. In one implementation, the high-speed controller 708 iscoupled to memory 704, display 716 (e.g., through a graphics processoror accelerator), and to high-speed expansion ports 710, which may acceptvarious expansion cards (not shown). In the implementation, low-speedcontroller 712 is coupled to storage device 706 and low-speed expansionport 714. The low-speed expansion port, which may include variouscommunication ports (e.g., USB, Bluetooth, Ethernet, wireless Ethernet)may be coupled to one or more input/output devices, such as a keyboard,a pointing device, a scanner, or a networking device such as a switch orrouter, e.g., through a network adapter.

The computing device 700 may be implemented in a number of differentforms, as shown in the figure. For example, it may be implemented as astandard server 720, or multiple times in a group of such servers. Itmay also be implemented as part of a rack server system 724. Inaddition, it may be implemented in a personal computer such as a laptopcomputer 722. Alternatively, components from computing device 700 may becombined with other components in a mobile device (not shown), such asdevice 750. Each of such devices may contain one or more of computingdevice 700, 750, and an entire system may be made up of multiplecomputing devices 700, 750 communicating with each other.

Computing device 750 includes a processor 752, memory 764, aninput/output device such as a display 754, a communication interface766, and a transceiver 768, among other components. The device 750 mayalso be provided with a storage device, such as a microdrive or otherdevice, to provide additional storage. Each of the components 750, 752,764, 754, 766, and 768, are interconnected using various buses, andseveral of the components may be mounted on a common motherboard or inother manners as appropriate.

The processor 752 can process instructions for execution within thecomputing device 750, including instructions stored in the memory 764.The processor may also include separate analog and digital processors.The processor may provide, for example, for coordination of the othercomponents of the device 750, such as control of user interfaces,applications run by device 750, and wireless communication by device750.

Processor 752 may communicate with a user through control interface 758and display interface 756 coupled to a display 754. The display 754 maybe, for example, a TFT LCD display or an OLED display, or otherappropriate display technology. The display interface 756 may compriseappropriate circuitry for driving the display 754 to present graphicaland other information to a user. The control interface 758 may receivecommands from a user and convert them for submission to the processor752. In addition, an external interface 762 may be provide incommunication with processor 752, so as to enable near areacommunication of device 750 with other devices. External interface 762may provide, for example, for wired communication (e.g., via a dockingprocedure) or for wireless communication (e.g., via Bluetooth or othersuch technologies).

The memory 764 stores information within the computing device 750. Inone implementation, the memory 764 is a computer-readable medium. In oneimplementation, the memory 764 is a volatile memory unit or units. Inanother implementation, the memory 764 is a non-volatile memory unit orunits. Expansion memory 774 may also be provided and connected to device750 through expansion interface 772, which may include, for example, aSIMM card interface. Such expansion memory 774 may provide extra storagespace for device 750, or may also store applications or otherinformation for device 750. Specifically, expansion memory 774 mayinclude instructions to carry out or supplement the processes describedabove, and may include secure information also. Thus, for example,expansion memory 774 may be provide as a security module for device 750,and may be programmed with instructions that permit secure use of device750. In addition, secure applications may be provided via the SIMMcards, along with additional information, such as placing identifyinginformation on the SIMM card in a non-hackable manner.

The memory may include for example, flash memory and/or MRAM memory, asdiscussed below. In one implementation, a computer program product istangibly embodied in an information carrier. The computer programproduct contains instructions that, when executed, perform one or moremethods, such as those described above. The information carrier is acomputer- or machine-readable medium, such as the memory 764, expansionmemory 774, memory on processor 752, or a propagated signal.

Device 750 may communicate wirelessly through communication interface766, which may include digital signal processing circuitry wherenecessary. Communication interface 766 may provide for communicationsunder various modes or protocols, such as GSM voice calls, SMS, EMS, orMMS messaging, CDMA, TDMA, PDC, WCDMA, CDMA2000, or GPRS, among others.Such communication may occur, for example, through radio-frequencytransceiver 768. In addition, short-range communication may occur, suchas using a Bluetooth, WiFi, or other such transceiver (not shown). Inaddition, GPS receiver module 770 may provide additional wireless datato device 750, which may be used as appropriate by applications runningon device 750.

Device 750 may also communication audibly using audio codec 760, whichmay receive spoken information from a user and convert it to usabledigital information. Audio codex 760 may likewise generate audible soundfor a user, such as through a speaker, e.g., in a handset of device 750.Such sound may include sound from voice telephone calls, may includerecorded sound (e.g., voice messages, music files, etc.) and may alsoinclude sound generated by applications operating on device 750.

The computing device 750 may be implemented in a number of differentforms, as shown in the figure. For example, the device 750 may beimplemented as a cellular telephone 780. The device 750 may also beimplemented as part of a smartphone 782, personal digital assistant, orother mobile device.

Where appropriate, the systems and the functional operations describedin this specification can be implemented in digital electroniccircuitry, or in computer software, firmware, or hardware, including thestructural means disclosed in this specification and structuralequivalents thereof, or in combinations of them. The techniques can beimplemented as one or more computer program products, i.e., one or morecomputer programs tangibly embodied in an information carrier, e.g., ina machine readable storage device or in a propagated signal, forexecution by, or to control the operation of, data processing apparatus,e.g., a programmable processor, a computer, or multiple computers. Acomputer program (also known as a program, software, softwareapplication, or code) can be written in any form of programminglanguage, including compiled or interpreted languages, and it can bedeployed in any form, including as a stand alone program or as a module,component, subroutine, or other unit suitable for use in a computingenvironment. A computer program does not necessarily correspond to afile. A program can be stored in a portion of a file that holds otherprograms or data, in a single file dedicated to the program in question,or in multiple coordinated files (e.g., files that store one or moremodules, sub programs, or portions of code). A computer program can bedeployed to be executed on one computer or on multiple computers at onesite or distributed across multiple sites and interconnected by acommunication network.

The processes and logic flows described in this specification can beperformed by one or more programmable processors executing one or morecomputer programs to perform the described functions by operating oninput data and generating output. The processes and logic flows can alsobe performed by, and apparatus can be implemented as, special purposelogic circuitry, e.g., an FPGA (field programmable gate array) or anASIC (application specific integrated circuit).

Processors suitable for the execution of a computer program include, byway of example, both general and special purpose microprocessors, andany one or more processors of any kind of digital computer. Generally,the processor will receive instructions and data from a read only memoryor a random access memory or both. The essential elements of a computerare a processor for executing instructions and one or more memorydevices for storing instructions and data. Generally, a computer willalso include, or be operatively coupled to receive data from or transferdata to, or both, one or more mass storage devices for storing data,e.g., magnetic, magneto optical disks, or optical disks. Informationcarriers suitable for embodying computer program instructions and datainclude all forms of non volatile memory, including by way of examplesemiconductor memory devices, e.g., EPROM, EEPROM, and flash memorydevices; magnetic disks, e.g., internal hard disks or removable disks;magneto optical disks; and CD ROM and DVD-ROM disks. The processor andthe memory can be supplemented by, or incorporated in, special purposelogic circuitry.

To provide for interaction with a user, aspects of the describedtechniques can be implemented on a computer having a display device,e.g., a CRT (cathode ray tube) or LCD (liquid crystal display) monitor,for displaying information to the user and a keyboard and a pointingdevice, e.g., a mouse or a trackball, by which the user can provideinput to the computer. Other kinds of devices can be used to provide forinteraction with a user as well; for example, feedback provided to theuser can be any form of sensory feedback, e.g., visual feedback,auditory feedback, or tactile feedback; and input from the user can bereceived in any form, including acoustic, speech, or tactile input.

The techniques can be implemented in a computing system that includes aback-end component, e.g., as a data server, or that includes amiddleware component, e.g., an application server, or that includes afront-end component, e.g., a client computer having a graphical userinterface or a Web browser through which a user can interact with animplementation, or any combination of such back-end, middleware, orfront-end components. The components of the system can be interconnectedby any form or medium of digital data communication, e.g., acommunication network. Examples of communication networks includepoint-to-point connections such as universal serial bus (USB) devices orUSB hubs, a local area network (“LAN”), and a wide area network (“WAN”),e.g., the Internet.

The computing system can include clients and servers. A client andserver are generally remote from each other and typically interactthrough a communication network. The relationship of client and serverarises by virtue of computer programs running on the respectivecomputers and having a client-server relationship to each other.

While this specification contains many specifics, these should not beconstrued as limitations on the scope of the invention or of what may beclaimed, but rather as descriptions of features specific to particularembodiments of the invention. Certain features that are described inthis specification in the context of separate embodiments can also beimplemented in combination in a single embodiment. Conversely, variousfeatures that are described in the context of a single embodiment canalso be implemented in multiple embodiments separately or in anysuitable subcombination. Moreover, although features may be describedabove as acting in certain combinations and even initially claimed assuch, one or more features from a claimed combination can in some casesbe excised from the combination, and the claimed combination may bedirected to a subcombination or variation of a subcombination.

Similarly, while operations are depicted in the drawings in a particularorder, this should not be understood as requiring that such operationsbe performed in the particular order shown or in sequential order, orthat all illustrated operations be performed, to achieve desirableresults. In certain circumstances, multitasking and parallel processingmay be advantageous. Moreover, the separation of various systemcomponents in the embodiments described above should not be understoodas requiring such separation in all embodiments, and it should beunderstood that the described program components and systems cangenerally be integrated together in a single software product orpackaged into multiple software products.

A number of embodiments have been described. Nevertheless, it will beunderstood that various modifications may be made without departing fromthe spirit and scope of the described embodiments. For example, thetriggering events (e.g., motion, sound, infrared detection) describedabove can be used to further lower the power consumption of the wirelesscamera. In many situations video surveillance cameras are placed inareas where there is very little motion for many hours. In these cases,significant energy savings can be gained by reducing the rate of any orall of the following functions: image capture, image compression, imagetransmission, based on a determination that motion has ceased.

In certain implementations, the motion detection can use an externalsensor or can be achieved by an algorithm that carries out an analysisof changes between captured images. The algorithm can be implemented inthe camera, or in the base station. In some cases, the motion detectionprocessing can be distributed between the camera and the base station.In the case where parts or the entire algorithm is implemented in thebase station, information regarding the motion sensing processing can betransferred to the camera by a secondary, low bandwidth radio link. Anexample of such an algorithm can be found in “BayesianIllumination-Invariant Motion Detection” by Til Aach and Lutz Dumbgenand Rudolf Mester and Daniel Toth, as described in Vol. III pages640-643 of Proceedings IEEE International Conference on Image Processing(ICIP).

For example, suppose that a wireless video surveillance camera, asdescribed above, is in a fast image capturing mode. This means that thewireless camera is capturing, compressing, and transmitting images at ahigh capture rate. A motion detection algorithm can be used to processesthe captured image data to determine if there has been motion in thefield of view. If at any time the motion detection algorithm determinesthat there is no motion in the field of view (based on a certainthreshold level of probability and criteria), then the camera can entera slow capture mode and a period of slower capture rate can beinitiated.

On the other hand, if the motion detection algorithm determines thatmotion persists in the field of view, the wireless network camera systemcontinues to capture images at the higher rate. Similarly, during a slowcapture mode, the motion detection algorithm can be used to initiate afast capture mode if motion has been detected.

The amount of energy saving based on the motion detection can beillustrated by analyzing a specific example camera system. Suppose thatfor a specific camera system, during the fast capture mode the cameraoperates at 3 frames per second (fps) and consumes 2 mJ per frame.Therefore, the average power dissipation during this fast capture modeis 3 frs×2 mJ per frame=6 mW. Suppose that during the slow capture modethe camera captures one frame every 5 seconds (0.2 lbs) and consumes 1.5mJ per frame. Therefore, the average power dissipation during this slowcapture mode is 0.2 fps×1.5 mJ per frame=0.3 mW.

Further suppose that motion is detected 20% of the time overall. Thenthe sustained average power consumption of the camera in operation willbe (20%×6+80%×0.3)=1.44 mW. This is clearly lower power then if thecamera were operating in the fast capture mode continuously, which canlead to a sustained average power dissipation of 6 mW during cameraoperation.

Motion, Activity and Object Detection Processing by the Base Station

In some implementations, the motion detection algorithm can be performedin the base station, and significant power saving benefits can beachieved because the camera is not used to carry out potentiallypower-intensive and complex algorithms. In addition, complex andcomprehensive algorithms or video analytics can be performed because thebase station can have access to more power and more computationalresources. In this manner, detection of additional triggering eventsbeyond simple motion and other categories such as object recognition canbe achieved. These more comprehensive and complex algorithms can havethe potential benefit of increasing the accuracy and reliability of thetriggering event detection and reducing probability of false detectionsor missing activity, objects or events. Examples of these types ofalgorithms can be seen in, for example, software products like Xprotect™from the Milestone Systems A/S Corporation.

User Alerts

In other implementations, the base station can initiate automatedcellular phone text messages, phone calls, emails and other textual,visual, or auditory alerts to the user based on a triggering event. Thetriggering event can be initiated as a result of motion detectionthrough ultrasonic, infrared, acoustic or electrical switch/relaytripping. The triggering event can also be based on the video imageprocessing described above. This message alert capability can avoid theneed for the user to constantly monitor the video stream for atriggering event.

Base Station Control or End User Control of Image Capture Rate

In further implementations, the base station can alter the image capturerate in response to information or control data from a client devicewhich is pulling images from the base station. For example, the clientmay distinguish between “active user observation” mode or“automatic/passive image capture” mode. During the “active userobservation mode,” the base station can receive information from aclient based on the fact that a user (human observer) is activelymonitoring or wishes to monitor the video stream. This information orcontrol data can be communicated to the base station and cause the basestation to increase the frame capture rate. During the“automatic/passive image capture mode,” the base station can receiveinformation or control data from the client because a network digitalvideo recording or other process is responsible for requesting images.Additionally, the base station can automatically determine the imagecapture rate based on activity or triggers detected by the camera or thebase station itself This detection of motion, or an object of interest,or a trigger activity can cause the base station to decrease the rate ofimage capture. Accordingly, other embodiments are within the scope ofthe following claims.

1. A wireless camera capable of generating a video signal andcomprising: a first radio configured to transmit said video signal to abase station over a wireless channel; and a second radio configured tooperate in a polling mode that reduces an average energy consumption ofsaid wireless camera, and configured to receive a request message fromsaid base station; wherein said base station reserves said wirelesschannel by transmitting on said wireless channel; wherein said firstradio transmits at least a portion of said video signal to said basestation at a known time in response to receiving said request message,and remains in a power down state until said base station reserves saidwireless channel; and wherein said wireless camera is powered at leastin part by an environmental energy source.
 2. The wireless camera ofclaim 1, wherein said environmental energy source is a solar cell. 3.The wireless camera of claim 1, wherein said base station is configuredto process said video signal into a processed video signal, and whereinsaid base station includes a web server to transmit said processed videosignal to a client.
 4. The wireless camera of claim 1, wherein saidfirst radio transmits using a spread spectrum modulation scheme.
 5. Thewireless camera of claim 1, wherein said wireless camera includes aninternal battery, said internal battery being configured to be rechargedby said environmental energy source.
 6. The wireless camera of claim 1,wherein a network connects said base station to a client.
 7. Thewireless camera of claim 1, wherein said first radio implements thephysical layer of the 802.11 standard.
 8. The wireless camera of claim1, wherein a radio section of said second radio cycles from active tostandby while in said polling mode.
 9. The wireless camera of claim 1,wherein said first radio transmits using orthogonal frequency divisionmodulation (OFDM).
 10. A method for providing a video signal comprisingthe steps of: generating said video signal using a wireless camera, saidwireless camera having a first radio and a second radio, and saidwireless camera being powered at least in part by an environmentalenergy source; polling by using said second radio in a polling mode thatreduces an average energy consumption of said wireless camera; receivinga request message from a base station with said second radio, saidrequest message indicating said base station has reserved a wirelesschannel by transmitting on said wireless channel; maintaining said firstradio in a power down state until receiving said request message; andtransmitting at least a portion of said video signal to said basestation on said wireless channel at a known time using said first radioin response to receiving said request message.
 11. The method of claim10, further comprising the step of: transmitting at least a segment ofsaid video signal to a web server from said base station; wherein saidweb server provides said segment of said video signal for remoteviewing.
 12. The method of claim 10, wherein said environmental energysource is a solar cell.
 13. The method of claim 10, wherein said firstradio transmits using a spread spectrum modulation scheme.
 14. Themethod of claim 10, wherein said wireless camera includes an internalbattery, said internal battery being configured to be recharged by saidenvironmental energy source.
 15. The method of claim 10, wherein saidbase station is configured to process said video signal into a processedvideo signal, and wherein said base station includes a web server totransmit said processed video signal to a client.
 16. The method ofclaim 10, wherein a network connects said base station to a client. 17.The method of claim 10, wherein said first radio implements the physicallayer of the 802.11 standard.
 18. The method of claim 10, wherein aradio section of said second radio cycles from active to standby whilein said polling mode.
 19. The method of claim 10, wherein said firstradio transmits using orthogonal frequency division modulation (OFDM).20. A system for providing a video signal for remote viewing comprising:a wireless camera configured to generate a video signal, transmit saidvideo signal on a wireless channel using a first radio, and operate asecond radio in a polling mode that reduces an average energyconsumption of said wireless camera; and a base station configured toreserve said wireless channel by transmitting on said wireless channel,said base station being configured to transmit a request message to saidwireless camera when said wireless channel has been reserved; whereinsaid wireless camera is powered at least in part by an environmentalenergy source; and wherein said wireless camera transmits at least aportion of said video signal on said wireless channel to said basestation in response to receiving said request message.